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<TABLE style="width: 22em; font-size: 88%;" class="infobox">
  <TBODY>
  <TR>
    <TH style="text-align: center; font-size: 125%;" colSpan="2">Traffic 
      collision avoidance system</TH></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2"><A class="image" href="http://en.wikipedia.org/wiki/File:TCAS_Indicator.jpg"><IMG 
      alt="TCAS Indicator.jpg" src="Traffic%20collision%20avoidance%20system%20-%20Wikipedia,%20the%20free%20encyclopedia_files/300px-TCAS_Indicator.jpg" 
      width="300" height="283"></A></TD></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2">TCAS and IVSI cockpit display 
      (monochrome)</TD></TR></TBODY></TABLE>
<TABLE style="width: 22em; font-size: 88%;" class="infobox">
  <TBODY>
  <TR>
    <TH style="text-align: center; font-size: 125%;" colSpan="2"></TH></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2"><A class="image" href="http://en.wikipedia.org/wiki/File:Tcas_EU-Flysafe.jpg"><IMG 
      alt="Tcas EU-Flysafe.jpg" src="Traffic%20collision%20avoidance%20system%20-%20Wikipedia,%20the%20free%20encyclopedia_files/300px-Tcas_EU-Flysafe.jpg" 
      width="300" height="301"></A></TD></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2">TCAS and EHSI cockpit display 
      (colour)</TD></TR></TBODY></TABLE>
<P>A <B>traffic collision avoidance system</B> or <B>traffic alert and collision 
avoidance system</B> (both abbreviated as <B>TCAS</B>) is an <A class="mw-redirect" 
title="Aircraft collision avoidance systems" href="http://en.wikipedia.org/wiki/Aircraft_collision_avoidance_systems">aircraft 
collision avoidance system</A> designed to reduce the incidence of mid-air 
collisions between aircraft. It monitors the airspace around an aircraft for 
other aircraft equipped with a corresponding active <A title="Transponder (aviation)" 
href="http://en.wikipedia.org/wiki/Transponder_(aviation)">transponder</A>, 
independent of <A title="Air traffic control" href="http://en.wikipedia.org/wiki/Air_traffic_control">air 
traffic control</A>, and warns pilots of the presence of other 
transponder-equipped aircraft which may present a threat of <A title="Mid-air collision" 
href="http://en.wikipedia.org/wiki/Mid-air_collision">mid-air collision</A> 
(MAC). It is a type of <A title="Airborne collision avoidance system" href="http://en.wikipedia.org/wiki/Airborne_collision_avoidance_system">airborne 
collision avoidance system</A> mandated by the <A title="International Civil Aviation Organization" 
href="http://en.wikipedia.org/wiki/International_Civil_Aviation_Organization">International 
Civil Aviation Organization</A> to be fitted to all aircraft with a maximum 
take-off mass (MTOM) of over 5700&nbsp;kg (12,586&nbsp;lbs) or authorized to 
carry more than 19 passengers.</P>
<P>Official definition from PANS-ATM (Nov 2007): <A title="Airborne collision avoidance system" 
href="http://en.wikipedia.org/wiki/Airborne_collision_avoidance_system">ACAS</A> 
/ TCAS is an aircraft system based on <A title="Secondary surveillance radar" 
href="http://en.wikipedia.org/wiki/Secondary_surveillance_radar">secondary 
surveillance radar</A> (SSR) transponder signals, which operates independently 
of ground-based equipment to provide advice to the pilot on potential 
conflicting aircraft that are equipped with <A class="mw-redirect" title="Secondary Surveillance Radar" 
href="http://en.wikipedia.org/wiki/Secondary_Surveillance_Radar">SSR</A> <A 
title="Transponder (aviation)" href="http://en.wikipedia.org/wiki/Transponder_(aviation)">transponders</A>.</P>
<P>In modern <A title="Glass cockpit" href="http://en.wikipedia.org/wiki/Glass_cockpit">glass 
cockpit</A> aircraft, the TCAS display may be integrated in the Navigation 
Display (ND) or Electronic Horizontal Situation Indicator (EHSI); in older glass 
cockpit aircraft and those with mechanical instrumentation, such an integrated 
TCAS display may replace the mechanical Vertical Speed Indicator (which 
indicates the rate with which the aircraft is descending or climbing).</P>
<TABLE id="toc" class="toc">
  <TBODY>
  <TR>
    <TD>
      <DIV id="toctitle">
      <H2>Contents</H2></DIV>
      <UL>
        <LI class="toclevel-1 tocsection-1"><A href="http://en.wikipedia.org/wiki/TCAS#Impetus_for_a_collision_prevention_system"><SPAN 
        class="tocnumber">1</SPAN> <SPAN class="toctext">Impetus for a collision 
        prevention system</SPAN></A></LI>
        <LI class="toclevel-1 tocsection-2"><A href="http://en.wikipedia.org/wiki/TCAS#TCAS_basics"><SPAN 
        class="tocnumber">2</SPAN> <SPAN class="toctext">TCAS basics</SPAN></A>
        <UL>
          <LI class="toclevel-2 tocsection-3"><A href="http://en.wikipedia.org/wiki/TCAS#System_description"><SPAN 
          class="tocnumber">2.1</SPAN> <SPAN class="toctext">System 
          description</SPAN></A></LI>
          <LI class="toclevel-2 tocsection-4"><A href="http://en.wikipedia.org/wiki/TCAS#System_components"><SPAN 
          class="tocnumber">2.2</SPAN> <SPAN class="toctext">System 
          components</SPAN></A></LI></UL></LI>
        <LI class="toclevel-1 tocsection-5"><A href="http://en.wikipedia.org/wiki/TCAS#TCAS_operation"><SPAN 
        class="tocnumber">3</SPAN> <SPAN class="toctext">TCAS 
        operation</SPAN></A>
        <UL>
          <LI class="toclevel-2 tocsection-6"><A href="http://en.wikipedia.org/wiki/TCAS#TCAS_operation_modes"><SPAN 
          class="tocnumber">3.1</SPAN> <SPAN class="toctext">TCAS operation 
          modes</SPAN></A></LI>
          <LI class="toclevel-2 tocsection-7"><A href="http://en.wikipedia.org/wiki/TCAS#TCAS_alerts"><SPAN 
          class="tocnumber">3.2</SPAN> <SPAN class="toctext">TCAS 
          alerts</SPAN></A></LI>
          <LI class="toclevel-2 tocsection-8"><A href="http://en.wikipedia.org/wiki/TCAS#Types_of_traffic_and_resolution_advisories"><SPAN 
          class="tocnumber">3.3</SPAN> <SPAN class="toctext">Types of traffic 
          and resolution advisories</SPAN></A></LI>
          <LI class="toclevel-2 tocsection-9"><A href="http://en.wikipedia.org/wiki/TCAS#Pilot.2Faircrew_interaction_during_a_TCAS_event"><SPAN 
          class="tocnumber">3.4</SPAN> <SPAN class="toctext">Pilot/aircrew 
          interaction during a TCAS event</SPAN></A></LI></UL></LI>
        <LI class="toclevel-1 tocsection-10"><A href="http://en.wikipedia.org/wiki/TCAS#Safety_aspects_of_TCAS"><SPAN 
        class="tocnumber">4</SPAN> <SPAN class="toctext">Safety aspects of 
        TCAS</SPAN></A></LI>
        <LI class="toclevel-1 tocsection-11"><A href="http://en.wikipedia.org/wiki/TCAS#Relationship_to_automatic_dependent_surveillance-broadcast_.28ADS-B.29"><SPAN 
        class="tocnumber">5</SPAN> <SPAN class="toctext">Relationship to 
        automatic dependent surveillance-broadcast (ADS-B)</SPAN></A></LI>
        <LI class="toclevel-1 tocsection-12"><A href="http://en.wikipedia.org/wiki/TCAS#Drawbacks_to_TCAS_and_ADS-B"><SPAN 
        class="tocnumber">6</SPAN> <SPAN class="toctext">Drawbacks to TCAS and 
        ADS-B</SPAN></A></LI>
        <LI class="toclevel-1 tocsection-13"><A href="http://en.wikipedia.org/wiki/TCAS#Versions_of_TCAS"><SPAN 
        class="tocnumber">7</SPAN> <SPAN class="toctext">Versions of 
        TCAS</SPAN></A>
        <UL>
          <LI class="toclevel-2 tocsection-14"><A href="http://en.wikipedia.org/wiki/TCAS#Passive"><SPAN 
          class="tocnumber">7.1</SPAN> <SPAN 
          class="toctext">Passive</SPAN></A></LI>
          <LI class="toclevel-2 tocsection-15"><A href="http://en.wikipedia.org/wiki/TCAS#TCAS_I"><SPAN 
          class="tocnumber">7.2</SPAN> <SPAN class="toctext">TCAS 
          I</SPAN></A></LI>
          <LI class="toclevel-2 tocsection-16"><A href="http://en.wikipedia.org/wiki/TCAS#TCAS_II"><SPAN 
          class="tocnumber">7.3</SPAN> <SPAN class="toctext">TCAS 
          II</SPAN></A></LI>
          <LI class="toclevel-2 tocsection-17"><A href="http://en.wikipedia.org/wiki/TCAS#TCAS_III"><SPAN 
          class="tocnumber">7.4</SPAN> <SPAN class="toctext">TCAS 
          III</SPAN></A></LI>
          <LI class="toclevel-2 tocsection-18"><A href="http://en.wikipedia.org/wiki/TCAS#TCAS_IV"><SPAN 
          class="tocnumber">7.5</SPAN> <SPAN class="toctext">TCAS 
          IV</SPAN></A></LI></UL></LI>
        <LI class="toclevel-1 tocsection-19"><A href="http://en.wikipedia.org/wiki/TCAS#Current_implementation"><SPAN 
        class="tocnumber">8</SPAN> <SPAN class="toctext">Current 
        implementation</SPAN></A>
        <UL>
          <LI class="toclevel-2 tocsection-20"><A href="http://en.wikipedia.org/wiki/TCAS#Current_TCAS_Limitations"><SPAN 
          class="tocnumber">8.1</SPAN> <SPAN class="toctext">Current TCAS 
          Limitations</SPAN></A></LI>
          <LI class="toclevel-2 tocsection-21"><A href="http://en.wikipedia.org/wiki/TCAS#Regulatory_situation_around_the_world"><SPAN 
          class="tocnumber">8.2</SPAN> <SPAN class="toctext">Regulatory 
          situation around the world</SPAN></A></LI></UL></LI>
        <LI class="toclevel-1 tocsection-22"><A href="http://en.wikipedia.org/wiki/TCAS#See_also"><SPAN 
        class="tocnumber">9</SPAN> <SPAN class="toctext">See 
        also</SPAN></A></LI>
        <LI class="toclevel-1 tocsection-23"><A href="http://en.wikipedia.org/wiki/TCAS#References"><SPAN 
        class="tocnumber">10</SPAN> <SPAN 
        class="toctext">References</SPAN></A></LI>
        <LI class="toclevel-1 tocsection-24"><A href="http://en.wikipedia.org/wiki/TCAS#External_links"><SPAN 
        class="tocnumber">11</SPAN> <SPAN class="toctext">External 
        links</SPAN></A></LI></UL></TD></TR></TBODY></TABLE>
<H2><SPAN class="editsection">[<A title="Edit section: Impetus for a collision prevention system" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=1">edit</A>]</SPAN> 
<SPAN id="Impetus_for_a_collision_prevention_system" class="mw-headline">Impetus 
for a collision prevention system</SPAN></H2>
<P>Research into collision avoidance systems has been ongoing since at least the 
1950s. <A class="mw-redirect" title="ICAO" href="http://en.wikipedia.org/wiki/ICAO">ICAO</A> 
and aviation authorities such as the <A title="Federal Aviation Administration" 
href="http://en.wikipedia.org/wiki/Federal_Aviation_Administration">Federal 
Aviation Administration</A> were spurred into action after several major mid-air 
collisions involving great loss of life.<SUP id="cite_ref-TCAS70_0-0" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TCAS71_1-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP> 
Some of these mid-air accidents include:</P>
<UL>
  <LI><A class="mw-redirect" title="United Airlines Flight 718" href="http://en.wikipedia.org/wiki/United_Airlines_Flight_718">Grand 
  Canyon midair collision</A> in 1956;</LI>
  <LI>The <A title="1960 New York air disaster" href="http://en.wikipedia.org/wiki/1960_New_York_air_disaster">New 
  York air disaster</A> in 1960;</LI>
  <LI>The <A title="Piedmont Airlines Flight 22" href="http://en.wikipedia.org/wiki/Piedmont_Airlines_Flight_22">Asheville 
  midair collision</A> in 1967;</LI>
  <LI>The <A title="1976 Zagreb mid-air collision" href="http://en.wikipedia.org/wiki/1976_Zagreb_mid-air_collision">Zagreb 
  mid-air collision</A> in 1976;</LI>
  <LI><A title="PSA Flight 182" href="http://en.wikipedia.org/wiki/PSA_Flight_182">PSA 
  Flight 182</A>, a <A title="Boeing 727" href="http://en.wikipedia.org/wiki/Boeing_727">Boeing 
  727</A> which collided with a <A title="Cessna 172" href="http://en.wikipedia.org/wiki/Cessna_172">Cessna 
  172</A> in 1978;</LI>
  <LI>The <A class="mw-redirect" title="1979 Ukraine Aeroflot mid-air collision" 
  href="http://en.wikipedia.org/wiki/1979_Ukraine_Aeroflot_mid-air_collision">Ukraine 
  Aeroflot mid-air collision</A>, between two <A title="Tupolev Tu-134" href="http://en.wikipedia.org/wiki/Tupolev_Tu-134">Tupolev 
  Tu-134</A> in 1979;</LI>
  <LI><A title="Aeroméxico Flight 498" href="http://en.wikipedia.org/wiki/Aerom%C3%A9xico_Flight_498">Aeroméxico 
  Flight 498</A>, a 1986 collision similar to <A title="PSA Flight 182" href="http://en.wikipedia.org/wiki/PSA_Flight_182">PSA 
  Flight 182</A>, which finally spurred the <A class="mw-redirect" title="US Congress" 
  href="http://en.wikipedia.org/wiki/US_Congress">US Congress</A> and other 
  regulatory bodies into action and led to mandatory collision avoidance 
  equipment.</LI>
  <LI><A class="mw-redirect" title="Saudi Arabian Airlines Flight 763" href="http://en.wikipedia.org/wiki/Saudi_Arabian_Airlines_Flight_763">Chakri 
  Dadri midair collision</A> over a town near <A title="New Delhi" href="http://en.wikipedia.org/wiki/New_Delhi">New 
  Delhi</A>, <A title="India" 
  href="http://en.wikipedia.org/wiki/India">India</A> in 1996;</LI></UL>
<P>The implementation of TCAS added a safety barrier to help prevent mid-air 
collisions. However, further study, refinements, training and regulatory 
measures were still required, because the limitations and misuse of the system 
still resulted in other incidents and fatal accidents, which include:</P>
<UL>
  <LI>The <A title="2001 Japan Airlines mid-air incident" href="http://en.wikipedia.org/wiki/2001_Japan_Airlines_mid-air_incident">Japan 
  Airlines near-miss incident</A> in 2001;</LI>
  <LI>The <A title="2002 Überlingen mid-air collision" href="http://en.wikipedia.org/wiki/2002_%C3%9Cberlingen_mid-air_collision">Überlingen 
  mid-air collision</A>, between a <A title="Boeing 757" href="http://en.wikipedia.org/wiki/Boeing_757">Boeing 
  757</A> and a <A title="Tupolev Tu-154" href="http://en.wikipedia.org/wiki/Tupolev_Tu-154">Tupolev 
  Tu-154</A> in 2002, where the Tupolev pilots declined to follow their TCAS 
  resolution advisory (RA), instead following the directions of the air traffic 
  controller, while the Boeing pilots followed their TCAS RA. having no ATC 
  instruction. By the time the crews of the two planes actually saw each other, 
  it was too late and the planes collided, killing 71;</LI>
  <LI>The <A title="Gol Transportes Aéreos Flight 1907" href="http://en.wikipedia.org/wiki/Gol_Transportes_A%C3%A9reos_Flight_1907">Gol 
  Flight 1907</A> collision with an <A title="Embraer Legacy 600" href="http://en.wikipedia.org/wiki/Embraer_Legacy_600">Embraer 
  Legacy 600</A> in 2006;</LI></UL>
<DIV class="dablink">For more examples, see <A title="Category:Mid-air collisions" 
href="http://en.wikipedia.org/wiki/Category:Mid-air_collisions">Category:Mid-air 
collisions</A>.</DIV>
<H2><SPAN class="editsection">[<A title="Edit section: TCAS basics" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=2">edit</A>]</SPAN> 
<SPAN id="TCAS_basics" class="mw-headline">TCAS basics</SPAN></H2>
<H3><SPAN class="editsection">[<A title="Edit section: System description" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=3">edit</A>]</SPAN> 
<SPAN id="System_description" class="mw-headline">System description</SPAN></H3>
<P>TCAS involves communication between all aircraft equipped with an appropriate 
<A title="Transponder (aviation)" href="http://en.wikipedia.org/wiki/Transponder_(aviation)">transponder</A> 
(provided the transponder is enabled and set up properly). Each TCAS-equipped 
aircraft interrogates all other aircraft in a determined range about their 
position (via the 1,030&nbsp;<A class="mw-redirect" title="MHz" href="http://en.wikipedia.org/wiki/MHz">MHz</A> 
<A title="Radio" href="http://en.wikipedia.org/wiki/Radio">radio</A> <A title="Frequency" 
href="http://en.wikipedia.org/wiki/Frequency">frequency</A>), and all other 
craft reply to other interrogations (via 1,090&nbsp;MHz). This 
interrogation-and-response cycle may occur several times per second.<SUP id="cite_ref-TCAS70_0-1" 
class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TCAS71_1-1" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP></P>
<P>The TCAS system builds a three dimensional map of aircraft in the airspace, 
incorporating their range (garnered from the interrogation and response round 
trip time), altitude (as reported by the interrogated aircraft), and bearing (by 
the directional antenna from the response). Then, by <A class="mw-redirect" 
title="Extrapolating" 
href="http://en.wikipedia.org/wiki/Extrapolating">extrapolating</A> current 
range and altitude difference to anticipated future values, it determines if a 
potential collision threat exists.</P>
<P>TCAS and its variants are only able to interact with aircraft that have a 
correctly operating mode C or mode S transponder. A unique 24-bit identifier is 
assigned to each aircraft that has a mode S transponder <A title="Identification friend or foe" 
href="http://en.wikipedia.org/wiki/Identification_friend_or_foe#Modes">Identification 
friend or foe#Modes</A>.</P>
<P>The next step beyond identifying potential collisions is automatically 
negotiating a mutual avoidance maneuver (currently, maneuvers are restricted to 
changes in altitude and modification of climb/sink rates) between the two (or 
more) conflicting aircraft. These avoidance maneuvers are communicated to the 
flight crew by a cockpit display and by synthesized voice instructions.<SUP id="cite_ref-TCAS70_0-2" 
class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TCAS71_1-2" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP></P>
<P>A protected volume of airspace surrounds each TCAS equipped aircraft. The 
size of the protected volume depends on the altitude, speed, and heading of the 
aircraft involved in the encounter. The illustration below gives an example of a 
typical TCAS protection volume.</P>
<DIV class="center">
<DIV class="floatnone"><A class="image" title="TCAS Volume" href="http://en.wikipedia.org/wiki/File:TCAS_Volume.jpg"><IMG 
alt="TCAS Volume" src="Traffic%20collision%20avoidance%20system%20-%20Wikipedia,%20the%20free%20encyclopedia_files/TCAS_Volume.jpg" 
width="549" height="466"></A></DIV></DIV>
<H3><SPAN class="editsection">[<A title="Edit section: System components" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=4">edit</A>]</SPAN> 
<SPAN id="System_components" class="mw-headline">System components</SPAN></H3>
<P>A TCAS installation consists of the following components:<SUP id="cite_ref-TCAS70_0-3" 
class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TCAS71_1-3" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP></P>
<DL>
  <DT>TCAS computer unit</DT>
  <DD>Performs airspace surveillance, intruder tracking, its own aircraft 
  altitude tracking, threat detection, RA maneuver determination and selection, 
  and generation of advisories. The TCAS Processor uses pressure altitude, radar 
  altitude, and discrete aircraft status inputs from its own aircraft to control 
  the collision avoidance logic parameters that determine the protection volume 
  around the TCAS aircraft.</DD>
  <DT>Antennas</DT>
  <DD>The antennas used by TCAS II include a directional antenna that is mounted 
  on the top of the aircraft and either an omnidirectional or a directional 
  antenna mounted on the bottom of the aircraft. Most installations use the 
  optional directional antenna on the bottom of the aircraft. In addition to the 
  two TCAS antennas, two antennas are also required for the Mode S transponder. 
  One antenna is mounted on the top of the aircraft while the other is mounted 
  on the bottom. These antennas enable the Mode S transponder to receive 
  interrogations at 1030&nbsp;MHz and reply to the received interrogations at 
  1090&nbsp;MHz.</DD>
  <DT>Cockpit presentation</DT>
  <DD>The TCAS interface with the pilots is provided by two displays: the 
  traffic display and the RA display. These two displays can be implemented in a 
  number of ways, including displays that incorporate both displays into a 
  single, physical unit. Regardless of the implementation, the information 
  displayed is identical. The standards for both the traffic display and the RA 
  display are defined in DO-185A.<SUP id="cite_ref-DO-185_2-0" 
  class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-DO-185-2"><SPAN>[</SPAN>3<SPAN>]</SPAN></A></SUP></DD>
</DL>
<H2><SPAN class="editsection">[<A title="Edit section: TCAS operation" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=5">edit</A>]</SPAN> 
<SPAN id="TCAS_operation" class="mw-headline">TCAS operation</SPAN></H2>
<P>The following section describes the TCAS operation based on TCAS II, since 
this is the version that has been adopted as an international standard (ACAS II) 
by ICAO and aviation authorities worldwide.<SUP id="cite_ref-TCAS70_0-4" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TCAS71_1-4" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP></P>
<H3><SPAN class="editsection">[<A title="Edit section: TCAS operation modes" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=6">edit</A>]</SPAN> 
<SPAN id="TCAS_operation_modes" class="mw-headline">TCAS operation 
modes</SPAN></H3>
<P>TCAS II can be currently operated in the following modes:<SUP id="cite_ref-TCAS70_0-5" 
class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TCAS71_1-5" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP></P>
<DL>
  <DT>Stand-by</DT>
  <DD>Power is applied to the TCAS Processor and the mode S transponder, but 
  TCAS does not issue any interrogations and the transponder will reply to only 
  discrete interrogations.</DD>
  <DT>Transponder</DT>
  <DD>The mode S transponder is fully operational and will reply to all 
  appropriate ground and TCAS interrogations. TCAS remains in stand-by.</DD>
  <DT>Traffic advisories only</DT>
  <DD>The mode S transponder is fully operational. TCAS will operate normally 
  and issue the appropriate interrogations and perform all tracking functions. 
  However, TCAS will only issue traffic advisories (TA), and the resolution 
  advisories (RA) will be inhibited.</DD>
  <DT>Automatic (traffic/resolution advisories)</DT>
  <DD>The mode S transponder is fully operational. TCAS will operate normally 
  and issue the appropriate interrogations and perform all tracking functions. 
  TCAS will issue traffic advisories (TA) and resolution advisories (RA), when 
  appropriate.</DD></DL>
<P>TCAS works in a coordinated manner, so when an RA is issued to conflicting 
aircraft, a required action (i.e., <I>Climb. Climb.</I>) has to be immediately 
performed by one of the aircraft, while the other one receives a similar RA in 
the opposite direction (i.e., <I>Descend. Descend.</I>).</P>
<H3><SPAN class="editsection">[<A title="Edit section: TCAS alerts" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=7">edit</A>]</SPAN> 
<SPAN id="TCAS_alerts" class="mw-headline">TCAS alerts</SPAN></H3>
<TABLE style="width: 22em; font-size: 88%;" class="infobox">
  <TBODY>
  <TR>
    <TH style="text-align: center; font-size: 125%;" colSpan="2"></TH></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2"><A class="image" href="http://en.wikipedia.org/wiki/File:TCAS_Envelope.JPG"><IMG 
      alt="TCAS Envelope.JPG" src="Traffic%20collision%20avoidance%20system%20-%20Wikipedia,%20the%20free%20encyclopedia_files/300px-TCAS_Envelope.jpg" 
      width="300" height="171"></A></TD></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2">TCAS II typical envelope</TD></TR>
  </TBODY></TABLE>
<TABLE style="width: 22em; font-size: 88%;" class="infobox">
  <TBODY>
  <TR>
    <TH style="text-align: center; font-size: 125%;" colSpan="2"></TH></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2"><A class="image" href="http://en.wikipedia.org/wiki/File:RA_types_table.jpg"><IMG 
      alt="RA types table.jpg" src="Traffic%20collision%20avoidance%20system%20-%20Wikipedia,%20the%20free%20encyclopedia_files/300px-RA_types_table.jpg" 
      width="300" height="181"></A></TD></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2">TCAS II types of RA</TD></TR>
  </TBODY></TABLE>
<P>TCAS II issues the following types of aural annunciations:</P>
<UL>
  <LI>Traffic advisory (TA)</LI>
  <LI>Resolution advisory (RA)</LI>
  <LI>Clear of conflict</LI></UL>
<P>When a TA is issued, pilots are instructed to initiate a visual search for 
the traffic causing the TA. If the traffic is visually acquired, pilots are 
instructed to maintain visual separation from the traffic. The pilot training 
programs also indicate that no horizontal maneuvers are to be made based solely 
on information shown on the traffic display. Slight adjustments in vertical 
speed while climbing or descending, or slight adjustments in airspeed while 
still complying with the ATC clearance are acceptable.<SUP id="cite_ref-DOC9863-6_3-0" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-DOC9863-6-3"><SPAN>[</SPAN>4<SPAN>]</SPAN></A></SUP></P>
<P>When an RA is issued, pilots are expected to respond immediately to the RA 
unless doing so would jeopardize the safe operation of the flight. This means 
that aircraft will at times have to manoeuver contrary to ATC instructions or 
disregard ATC instructions. In these cases, the controller is no longer 
responsible for separation of the aircraft involved in the RA until the conflict 
is terminated.</P>
<P>On the other hand, ATC can potentially interfere with the pilot’s response to 
RAs. If a conflicting ATC instruction coincides with an RA, the pilot may assume 
that ATC is fully aware of the situation and is providing the better resolution. 
But in reality ATC is not aware of the RA until the RA is reported by the pilot. 
Once the RA is reported by the pilot, ATC is required not to attempt to modify 
the flight path of the aircraft involved in the encounter. Hence, the pilot is 
expected to “follow the RA” but in practice this does not yet always happen.</P>
<P>Some States have implemented “RA downlink” which provides air traffic 
controllers with information about RAs posted in the cockpit obtained via Mode S 
radars. Currently, there are no ICAO provisions concerning the use of RA 
downlink by air traffic controllers.</P>
<P>The following points receive emphasis during pilot training:</P>
<UL>
  <LI>Do not manoeuver in a direction opposite to that indicated by the RA 
  because this may result in a collision.</LI>
  <LI>Inform the controller of the RA as soon as permitted by flight crew 
  workload after responding to the RA. There is no requirement to make this 
  notification prior to initiating the RA response.</LI>
  <LI>Be alert for the removal of RAs or the weakening of RAs so that deviations 
  from a cleared altitude are minimized.</LI>
  <LI>If possible, comply with the controller’s clearance, e.g. turn to 
  intercept an airway or localizer, at the same time as responding to an 
  RA.</LI>
  <LI>When the RA event is completed, promptly return to the previous ATC 
  clearance or instruction or comply with a revised ATC clearance or 
  instruction.<SUP id="cite_ref-DOC9863-6_3-1" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-DOC9863-6-3"><SPAN>[</SPAN>4<SPAN>]</SPAN></A></SUP></LI>
</UL>
<H3><SPAN class="editsection">[<A title="Edit section: Types of traffic and resolution advisories" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=8">edit</A>]</SPAN> 
<SPAN id="Types_of_traffic_and_resolution_advisories" class="mw-headline">Types 
of traffic and resolution advisories</SPAN></H3>
<TABLE class="wikitable">
  <TBODY>
  <TR>
    <TH>Type</TH>
    <TH>Text</TH>
    <TH>Meaning</TH>
    <TH>Required action<SUP id="cite_ref-TCAS70_0-6" class="reference"><A 
      href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
      id="cite_ref-TCAS71_1-6" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP><SUP 
      id="cite_ref-4" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-4"><SPAN>[</SPAN>5<SPAN>]</SPAN></A></SUP></TH>
  </TR>
  <TR>
    <TD>TA</TD>
    <TD><I>Traffic; traffic.</I></TD>
    <TD>Intruder near both horizontally and vertically.</TD>
    <TD>Attempt visual contact, and be prepared to maneuver if an RA 
    occurs.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Climb; climb.</I></TD>
    <TD>Intruder will pass below</TD>
    <TD>Begin climbing at 1500–2000&nbsp;ft/min</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Descend. Descend.</I></TD>
    <TD>Intruder will pass above.</TD>
    <TD>Begin descending at 1500–2000&nbsp;ft/min</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Increase climb.</I></TD>
    <TD>Intruder will pass just below</TD>
    <TD>Climb at 2500 – 3000&nbsp;ft/min.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Increase descent.</I></TD>
    <TD>Intruder will pass just above.</TD>
    <TD>Descend at 2500 – 3000&nbsp;ft/min.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Reduce climb.</I></TD>
    <TD>Intruder is probably well below.</TD>
    <TD>Climb at a slower rate.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Reduce descent.</I></TD>
    <TD>Intruder is probably well above.</TD>
    <TD>Descend at a slower rate.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Climb; climb now.</I></TD>
    <TD>Intruder that was passing above, will now pass below.</TD>
    <TD>Change from a descent to a climb.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Descend; descend now.</I></TD>
    <TD>Intruder that was passing below, will now pass above.</TD>
    <TD>Change from a climb to a descent.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Maintain vertical speed; maintain.</I></TD>
    <TD>Intruder will be avoided if vertical rate is maintained.</TD>
    <TD>Maintain current vertical rate.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Adjust vertical speed; adjust.</I></TD>
    <TD>Intruder considerably away, or weakening of initial RA.</TD>
    <TD>Begin to level off.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Monitor vertical speed.</I></TD>
    <TD>Intruder ahead in level flight, above or below.</TD>
    <TD>Remain in level flight.</TD></TR>
  <TR>
    <TD>RA</TD>
    <TD><I>Crossing.</I></TD>
    <TD>Passing through the intruder's level. Usually added to any other 
    RA.</TD>
    <TD>Proceed according to the associated RA.</TD></TR>
  <TR>
    <TD>CC</TD>
    <TD><I>Clear of conflict.</I></TD>
    <TD>Intruder is no longer a threat.</TD>
    <TD>Return promptly to previous ATC clearance.</TD></TR></TBODY></TABLE>
<H3><SPAN class="editsection">[<A title="Edit section: Pilot/aircrew interaction during a TCAS event" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=9">edit</A>]</SPAN> 
<SPAN id="Pilot.2Faircrew_interaction_during_a_TCAS_event" 
class="mw-headline">Pilot/aircrew interaction during a TCAS event</SPAN></H3>
<TABLE class="wikitable">
  <CAPTION>TCAS event interaction<SUP id="cite_ref-DOC9863-6_3-2" class="reference"><A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_note-DOC9863-6-3"><SPAN>[</SPAN>4<SPAN>]</SPAN></A></SUP></CAPTION>
  <TBODY>
  <TR vAlign="top">
    <TH>Aircrew</TH>
    <TH>Controller</TH></TR>
  <TR vAlign="top">
    <TH style="align: center;" colSpan="7"><B>Traffic advisory (TA)</B></TH></TR>
  <TR vAlign="top">
    <TD>Shall not manoeuver their aircraft in response to traffic advisories 
      (TAs) only</TD>
    <TD>Remains responsible for ATC separation</TD></TR>
  <TR vAlign="top">
    <TD>Should prepare for appropriate action if an RA occurs; but as far as 
      practicable, pilots should not request traffic information</TD>
    <TD>If requested by the aircrew, shall give traffic information</TD></TR>
  <TR vAlign="top">
    <TH style="align: center;" colSpan="7">Resolution advisory (RA)</TH></TR>
  <TR vAlign="top">
    <TD>Shall respond immediately and manoeuver as indicated, unless doing so 
      would jeopardize the safety of the airplane</TD>
    <TD>Shall not attempt to modify the flight path of an aircraft responding 
      to an RA</TD></TR>
  <TR vAlign="top">
    <TD>Shall follow the RA even if there is a conflict between the RA and an 
      Air Traffic Control (ATC) instruction to manoeuver</TD>
    <TD>Shall not issue any clearance or instruction to the aircraft involved 
      until the pilot reports returning to the terms of the assigned ATC 
      clearance or instruction</TD></TR>
  <TR vAlign="top">
    <TD>Shall never manoeuver in the opposite sense to an RA, nor maintain a 
      vertical rate in the opposite sense to an RA</TD>
    <TD>Shall acknowledge the report by using the phrase <I>"ROGER"</I></TD></TR>
  <TR vAlign="top">
    <TD>When deviating from an air traffic control instruction or clearance in 
      response to any RA, shall:
      <UL>
        <LI>As soon as permitted by flight crew workload, notify the appropriate 
        ATC unit of the deviation.</LI>
        <LI>Immediately inform ATC when they are unable to comply with a 
        clearance or instruction that conflicts with an RA.</LI></UL></TD>
    <TD>If requested by the aircrew, shall give traffic information</TD></TR>
  <TR vAlign="top">
    <TD>Shall promptly comply with any subsequent RAs issued by TCAS</TD>
    <TD>Ceases to be responsible for providing separation between that 
      aircraft and any other aircraft affected as a direct consequence of the 
      manoeuver induced by the RA</TD></TR>
  <TR vAlign="top">
    <TD>Shall limit the alterations of the flight path to the minimum extent 
      necessary to comply with the resolution advisories</TD>
    <TD></TD></TR>
  <TR vAlign="top">
    <TH style="align: center;" colSpan="7">Clear of conflict (CC)</TH></TR>
  <TR vAlign="top">
    <TD>Shall promptly return to the terms of the ATC instruction or clearance 
      when the conflict is resolved</TD>
    <TD>Shall resume responsibility for providing separation for all the 
      affected aircraft when he acknowledges:
      <UL>
        <LI>A report from the pilot that the aircraft is resuming the assigned 
        ATC clearance or instruction and issues an alternative clearance or 
        instruction which is acknowledged by the pilot</LI>
        <LI>A report from the pilot that the aircraft has resumed the assigned 
        ATC clearance or instruction</LI></UL></TD></TR>
  <TR vAlign="top">
    <TD>Shall notify ATC after initiating a return to or resuming the current 
      clearance</TD>
    <TD></TD></TR></TBODY></TABLE>
<H2><SPAN class="editsection">[<A title="Edit section: Safety aspects of TCAS" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=10">edit</A>]</SPAN> 
<SPAN id="Safety_aspects_of_TCAS" class="mw-headline">Safety aspects of 
TCAS</SPAN></H2>
<P>Safety studies on TCAS estimate that the system improves safety in the 
airspace by a factor of between 3 and 5.<SUP id="cite_ref-ACASA_5-0" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-ACASA-5"><SPAN>[</SPAN>6<SPAN>]</SPAN></A></SUP></P>
<P>However, it is well understood that part of the remaining risk is that TCAS 
may induce midair collisions: "In particular, it is dependent on the accuracy of 
the threat aircraft’s reported altitude and on the expectation that the threat 
aircraft will not make an abrupt maneuver that defeats the TCAS Resolution 
Advisory (RA). The safety study also shows that TCAS II will induce some 
critical near midair collisions..." (See page 7 of Introduction to TCAS II 
Version 7 and 7.1 (PDF) in external links below).<SUP id="cite_ref-TCAS70_0-7" 
class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TCAS71_1-7" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP></P>
<P>One potential problem with TCAS II is the possibility that a recommended 
avoidance maneuver might direct the flight crew to descend toward terrain below 
a safe altitude. Recent requirements for incorporation of ground proximity 
mitigate this risk. Ground proximity warning alerts have priority in the cockpit 
over TCAS alerts.</P>
<P>Some pilots have been unsure how to act when their aircraft was requested to 
climb whilst flying at their maximum altitude. The accepted procedure is to 
follow the climb RA as best as possible, temporarily trading speed for height. 
The climb RA should quickly finish. In the event of a stall warning, the stall 
warning would take priority.</P>
<P>Both cases have been already addressed by Version 7.0 of TCAS II and are 
currently handled by a corrective RA together with a visual indication of a 
green arc in the IVSI display to indicate the safe range for the climb or 
descent rate. However, it has been found that in some cases these indications 
could lead to a dangerous situation for the involved aircraft. For example, if a 
TCAS event occurs when two aircraft are descending one over the other for 
landing, the aircraft at the lower altitude will first receive a <I>"Descend, 
descend"</I> RA, and when reaching an extreme low altitude, this will change to 
a <I>"Adjust Vertical Speed, Adjust"</I> RA, together with a green arc 
indication directing the pilot to level off the aircraft. This could place the 
aircraft dangerously into the path of the intruder above, who is descending to 
land. A change proposal has been issued to correct this problem.<SUP id="cite_ref-CP116_6-0" 
class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-CP116-6"><SPAN>[</SPAN>7<SPAN>]</SPAN></A></SUP></P>
<H2><SPAN class="editsection">[<A title="Edit section: Relationship to automatic dependent surveillance-broadcast (ADS-B)" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=11">edit</A>]</SPAN> 
<SPAN id="Relationship_to_automatic_dependent_surveillance-broadcast_.28ADS-B.29" 
class="mw-headline">Relationship to automatic dependent surveillance-broadcast 
(ADS-B)</SPAN></H2>
<P><A title="Automatic dependent surveillance-broadcast" href="http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast">Automatic 
dependent surveillance-broadcast</A> (ADS-B) messages are transmitted from 
aircraft equipped with suitable transponders, containing information such as 
identity, location, and velocity. The signals are broadcast on the 1090&nbsp;MHz 
radio frequency. ADS-B messages are also carried on a Universal Access 
Transceiver (UAT) in the 978&nbsp;MHz band.<SUP id="cite_ref-ADS-B_UAT_7-0" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-ADS-B_UAT-7"><SPAN>[</SPAN>8<SPAN>]</SPAN></A></SUP></P>
<P>TCAS equipment which is capable of processing ADS-B messages may use this 
information to enhance the performance of TCAS, using techniques known as 
"hybrid surveillance". As currently implemented, hybrid surveillance uses 
reception of ADS-B messages from an aircraft to reduce the rate at which the 
TCAS equipment interrogates that aircraft. This reduction in interrogations 
reduces the use of the 1030/1090&nbsp;MHz radio channel, and will over time 
extend the operationally useful life of TCAS technology. The ADS-B messages will 
also allow low cost (for aircraft) technology to provide real time traffic in 
the cockpit for small aircraft. Currently UAT based traffic uplinks are provided 
in Alaska and in regions of the East coast of the USA.</P>
<P>Hybrid surveillance does not include the use any of the aircraft flight 
information in the TCAS conflict detection algorithms; ADS-B is used only to 
identify aircraft that can safely be interrogated at a lower rate.</P>
<P>In the future, prediction capabilities may be improved by using the state 
vector information present in ADS-B messages. Also, since ADS-B messages can be 
received at greater range than TCAS normally operates, aircraft can be acquired 
earlier by the TCAS tracking algorithms.</P>
<P>The identity information present in ADS-B messages can be used to label other 
aircraft on the cockpit display (where present), painting a picture similar to 
what an air traffic controller would see and improving situational 
awareness.<SUP id="cite_ref-8" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-8"><SPAN>[</SPAN>9<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TOR_ADS-B_9-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TOR_ADS-B-9"><SPAN>[</SPAN>10<SPAN>]</SPAN></A></SUP></P>
<H2><SPAN class="editsection">[<A title="Edit section: Drawbacks to TCAS and ADS-B" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=12">edit</A>]</SPAN> 
<SPAN id="Drawbacks_to_TCAS_and_ADS-B" class="mw-headline">Drawbacks to TCAS and 
ADS-B</SPAN></H2>
<P>The major demonstrated problem of the <A title="Automatic dependent surveillance-broadcast" 
href="http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast">ADS-B</A> 
protocol integration is this added verbosity of the extra information 
transmitted, which is considered unnecessary for collision avoidance purposes. 
The more data transmitted from one aircraft in accordance with the system 
design, the lesser the number of aircraft that can participate in the system, 
due to the fixed and limited channel data bandwidth (1 megabit/second with the 
26/64 data bits to packet length bit capacity of the Mode S downlink data format 
packet). For every Mode S message of 64 bits, the overhead demands 8 for clock 
sync at the receiver and Mode S packet discovery, 6 for type of Mode S packet, 
24 for who it came from. Since that leaves only 26 for information, multiple 
packets must be used to convey a single message. The <A title="Automatic dependent surveillance-broadcast" 
href="http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast">ADS-B</A> 
"fix" proposal is to go to a 128 bit packet, which is not an accepted 
international standard.<SUP id="cite_ref-ADS-B_UAT_7-1" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-ADS-B_UAT-7"><SPAN>[</SPAN>8<SPAN>]</SPAN></A></SUP> 
Either approach increases channel traffic above the level sustainable for 
environments such as the Los Angeles Basin.</P>
<H2><SPAN class="editsection">[<A title="Edit section: Versions of TCAS" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=13">edit</A>]</SPAN> 
<SPAN id="Versions_of_TCAS" class="mw-headline">Versions of TCAS</SPAN></H2>
<H3><SPAN class="editsection">[<A title="Edit section: Passive" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=14">edit</A>]</SPAN> 
<SPAN id="Passive" class="mw-headline">Passive</SPAN></H3>
<DIV class="rellink boilerplate seealso">See also: <A title="Portable Collision Avoidance System" 
href="http://en.wikipedia.org/wiki/Portable_Collision_Avoidance_System">Portable 
Collision Avoidance System</A></DIV>
<P>Collision Avoidance systems which rely on <A title="Transponder (aviation)" 
href="http://en.wikipedia.org/wiki/Transponder_(aviation)">transponder</A> 
replies triggered by ground and airborne systems are considered passive. Ground 
and airborne interrogators query nearby transponders for mode C altitude 
information, which can be monitored by third-party systems for traffic 
information. Passive systems display traffic similar to TCAS, however generally 
have a range of less than 7 nautical miles (13&nbsp;km).<SUP style="white-space: nowrap;" 
class="Template-Fact">[<I><A title="Wikipedia:Citation needed" href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed"><SPAN 
title="This claim needs references to reliable sources from January 2011">citation 
needed</SPAN></A></I>]</SUP></P>
<H3><SPAN class="editsection">[<A title="Edit section: TCAS I" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=15">edit</A>]</SPAN> 
<SPAN id="TCAS_I" class="mw-headline">TCAS I</SPAN></H3>
<P>TCAS I is the first generation of collision avoidance technology. It is 
cheaper but less capable than the modern TCAS II system, and is mainly intended 
for <A title="General aviation" href="http://en.wikipedia.org/wiki/General_aviation">general 
aviation</A> use. TCAS I systems are able to monitor the traffic situation 
around a plane (to a range of about 40 miles) and offer information on the 
approximate bearing and altitude of other aircraft. It can also generate 
collision warnings in the form of a "Traffic Advisory" (TA). The TA warns the 
pilot that another aircraft is in near vicinity, announcing <I>"Traffic, 
traffic"</I>, but does not offer any suggested remedy; it is up to the pilot to 
decide what to do, usually with the assistance of Air Traffic Control. When a 
threat has passed, the system announces <I>"Clear of conflict"</I>.<SUP id="cite_ref-FAA-TCAS_10-0" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-FAA-TCAS-10"><SPAN>[</SPAN>11<SPAN>]</SPAN></A></SUP></P>
<H3><SPAN class="editsection">[<A title="Edit section: TCAS II" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=16">edit</A>]</SPAN> 
<SPAN id="TCAS_II" class="mw-headline">TCAS II</SPAN></H3>
<TABLE style="width: 22em; font-size: 88%;" class="infobox">
  <TBODY>
  <TR>
    <TH style="text-align: center; font-size: 125%;" colSpan="2"></TH></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2"><A class="image" href="http://en.wikipedia.org/wiki/File:CP112E.jpg"><IMG 
      alt="CP112E.jpg" src="Traffic%20collision%20avoidance%20system%20-%20Wikipedia,%20the%20free%20encyclopedia_files/300px-CP112E.jpg" 
      width="300" height="167"></A></TD></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2">Change proposal CP112E 
      graphical explanation</TD></TR></TBODY></TABLE>
<TABLE style="width: 22em; font-size: 88%;" class="infobox">
  <TBODY>
  <TR>
    <TH style="text-align: center; font-size: 125%;" colSpan="2"></TH></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2"><A class="image" href="http://en.wikipedia.org/wiki/File:CP115.jpg"><IMG 
      alt="CP115.jpg" src="Traffic%20collision%20avoidance%20system%20-%20Wikipedia,%20the%20free%20encyclopedia_files/300px-CP115.jpg" 
      width="300" height="168"></A></TD></TR>
  <TR>
    <TD style="text-align: center;" colSpan="2">Change proposal CP115 
      graphical explanation</TD></TR></TBODY></TABLE>
<P>TCAS II is the second and current generation of instrument warning TCAS, used 
in the majority of <A title="Commercial aviation" href="http://en.wikipedia.org/wiki/Commercial_aviation">commercial 
aviation</A> aircraft (see table below). It offers all the benefits of TCAS I, 
but will also offer the pilot direct, vocalized instructions to avoid danger, 
known as a "Resolution Advisory" (RA). The suggestive action may be 
"corrective", suggesting the pilot change vertical speed by announcing, 
<I>"Descend, descend"</I>, <I>"Climb, climb"</I> or <I>"Adjust Vertical Speed 
Adjust"</I> (meaning reduce vertical speed). By contrast a "preventive" RA may 
be issued which simply warns the pilots not to deviate from their present 
vertical speed, announcing, <I>"Monitor vertical speed"</I> or <I>"Maintain 
vertical speed, Maintain"</I>. TCAS II systems coordinate their resolution 
advisories before issuing commands to the pilots, so that if one aircraft is 
instructed to descend, the other will typically be told to climb — maximising 
the separation between the two aircraft.<SUP id="cite_ref-TCAS70_0-8" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TCAS71_1-8" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP></P>
<P>As of 2006, the only implementation that meets the ACAS II standards set by 
<A class="mw-redirect" title="ICAO" 
href="http://en.wikipedia.org/wiki/ICAO">ICAO</A><SUP id="cite_ref-11" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-11"><SPAN>[</SPAN>12<SPAN>]</SPAN></A></SUP> 
was Version 7.0 of TCAS II<SUP id="cite_ref-TCAS70_0-9" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP>, 
produced by three avionics manufacturers: <A title="Rockwell Collins" href="http://en.wikipedia.org/wiki/Rockwell_Collins">Rockwell 
Collins</A>, <A title="Honeywell" 
href="http://en.wikipedia.org/wiki/Honeywell">Honeywell</A>, and ACSS (Aviation 
Communication &amp; Surveillance Systems; an <A title="L-3 Communications" href="http://en.wikipedia.org/wiki/L-3_Communications">L-3 
Communications</A> and <A title="Thales Group" href="http://en.wikipedia.org/wiki/Thales_Group">Thales 
Avionics</A> company).</P>
<P>After the <A class="mw-redirect" title="Bashkirian Airlines Flight 2937" 
href="http://en.wikipedia.org/wiki/Bashkirian_Airlines_Flight_2937">Überlingen 
mid-air collision</A> (July 1, 2002), studies have been made to improve TCAS II 
capabilities. Following extensive <A title="Eurocontrol" href="http://en.wikipedia.org/wiki/Eurocontrol">Eurocontrol</A> 
input and pressure, a revised TCAS II Minimum Operational Performance Standards 
(MOPS) document has been jointly developed by RTCA (Special Committee SC-147<SUP 
id="cite_ref-SC-147_12-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-SC-147-12"><SPAN>[</SPAN>13<SPAN>]</SPAN></A></SUP>) 
and EUROCAE. As a result, by 2008 the standards for Version 7.1 of TCAS II have 
been issued<SUP id="cite_ref-SIRE_13-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-SIRE-13"><SPAN>[</SPAN>14<SPAN>]</SPAN></A></SUP> 
and published as RTCA DO-185B<SUP id="cite_ref-DO-185_2-1" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-DO-185-2"><SPAN>[</SPAN>3<SPAN>]</SPAN></A></SUP> 
(June 2008) and EUROCAE ED-143 (September 2008).</P>
<P>TCAS II Version 7.1<SUP id="cite_ref-TCAS71_1-9" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP> 
will be able to issue RA reversals in coordinated encounters, in case one of the 
aircraft doesn't follow the original RA instructions (Change proposal 
CP112E).<SUP id="cite_ref-CP112E_14-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-CP112E-14"><SPAN>[</SPAN>15<SPAN>]</SPAN></A></SUP> 
Other changes in this version are the replacement of the ambiguous <I>"Adjust 
Vertical Speed, Adjust"</I> RA with the <I>"Level off, Level off"</I> RA, to 
prevent improper response by the pilots (Change proposal CP115).;<SUP id="cite_ref-CP115_15-0" 
class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-CP115-15"><SPAN>[</SPAN>16<SPAN>]</SPAN></A></SUP> 
and the improved handling of corrective/preventive annunciation and removal of 
green arc display when a positive RA weakens solely due to an extreme low or 
high altitude condition (1000 feet AGL or below, or near the aircraft top 
ceiling) to prevent incorrect and possibly dangerous guidance to the pilot 
(Change proposal CP116).<SUP id="cite_ref-CP116_6-1" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-CP116-6"><SPAN>[</SPAN>7<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-EUROTCAS71_16-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-EUROTCAS71-16"><SPAN>[</SPAN>17<SPAN>]</SPAN></A></SUP></P>
<P>Studies conducted for <A title="Eurocontrol" href="http://en.wikipedia.org/wiki/Eurocontrol">Eurocontrol</A>, 
using recently recorded operational data, indicate that currently the 
probability of a <A title="Mid-air collision" href="http://en.wikipedia.org/wiki/Mid-air_collision">mid-air 
collision</A> in European airspace is 2.7 x 10<SUP>−8</SUP> which equates to one 
in every 3 years. When TCAS II Version 7.1 is implemented, that probability will 
be reduced by a factor of 4.<SUP id="cite_ref-EUROTCAS71_16-1" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-EUROTCAS71-16"><SPAN>[</SPAN>17<SPAN>]</SPAN></A></SUP></P>
<H3><SPAN class="editsection">[<A title="Edit section: TCAS III" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=17">edit</A>]</SPAN> 
<SPAN id="TCAS_III" class="mw-headline">TCAS III</SPAN></H3>
<P>Originally designated TCAS II Enhanced, TCAS III was envisioned as an 
expansion of the TCAS II concept to include horizontal resolution advisory 
capability. TCAS III was the "next generation" of collision avoidance technology 
which underwent development by aviation companies such as <A title="Honeywell" 
href="http://en.wikipedia.org/wiki/Honeywell">Honeywell</A>. TCAS III 
incorporated technical upgrades to the TCAS II system, and had the capability to 
offer traffic advisories and resolve traffic conflicts using <I>horizontal</I> 
as well as vertical manouevring directives to pilots. For instance, in a head-on 
situation, one aircraft might be directed, "turn right, climb" while the other 
would be directed "turn right, descend." This would act to further increase the 
total separation between aircraft, in both horizontal and vertical aspects. 
Horizontal directives would be useful in a conflict between two aircraft close 
to the ground where there may be little if any vertical maneuvering space.<SUP 
id="cite_ref-TCASIII_17-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCASIII-17"><SPAN>[</SPAN>18<SPAN>]</SPAN></A></SUP></P>
<P>TCAS III attempts to use the TCAS directional antenna to assign a bearing to 
other aircraft, and thus be able to generate a horizontal maneuver (e.g. turn 
left or right). However, it was judged by the industry to be unfeasible due to 
limitations in the accuracy of the TCAS directional antennas. The directional 
antennas were judged not to be accurate enough to generate an accurate 
horizontal-plane position, and thus an accurate horizontal resolution. By 1995, 
years of testing and analysis determined that the concept was unworkable using 
available surveillance technology (due to the inadequacy of horizontal position 
information), and that horizontal RAs were unlikely to be invoked in most 
encounter geometries. Hence, all work on TCAS III was suspended and there are no 
plans for its implementation. The concept has later evolved and been replaced by 
TCAS IV.<SUP id="cite_ref-skybrary_18-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-skybrary-18"><SPAN>[</SPAN>19<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-sci_aeronautics_19-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-sci_aeronautics-19"><SPAN>[</SPAN>20<SPAN>]</SPAN></A></SUP></P>
<H3><SPAN class="editsection">[<A title="Edit section: TCAS IV" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=18">edit</A>]</SPAN> 
<SPAN id="TCAS_IV" class="mw-headline">TCAS IV</SPAN></H3>
<P>TCAS IV uses additional information encoded by the target aircraft in the 
Mode S <A title="Transponder (aviation)" href="http://en.wikipedia.org/wiki/Transponder_(aviation)">transponder</A> 
reply (i.e. target encodes its own position into the transponder signal) to 
generate a horizontal resolution to an RA. Obviously, this requires the target 
aircraft to have some data link capability at a minimum. In addition, some 
reliable source of position (such as <A title="Inertial navigation system" href="http://en.wikipedia.org/wiki/Inertial_navigation_system">Inertial 
Navigation System</A> or <A class="mw-redirect" title="GPS" href="http://en.wikipedia.org/wiki/GPS">GPS</A>) 
is needed on the target aircraft in order for it to be encoded.</P>
<P>TCAS IV has replaced the TCAS III concept by the mid 1990s. One of the 
results of TCAS III experience has been that the directional antenna used by the 
TCAS processor to assign a bearing to a received <A title="Transponder (aviation)" 
href="http://en.wikipedia.org/wiki/Transponder_(aviation)">transponder</A> reply 
is not accurate enough to generate an accurate horizontal position, and thus a 
safe horizontal resolution. TCAS IV uses additional position information encoded 
on an air-to-air data link to generate the bearing information, so the accuracy 
of the directional antenna would not be a factor.</P>
<P>TCAS IV development continued for some years, but the appearance of new 
trends in data link such as Automatic Dependent Surveillance - Broadcast (<A 
title="Automatic dependent surveillance-broadcast" href="http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast">ADS-B</A>) 
have pointed out a need to re-evaluate whether a data link system dedicated to 
collision avoidance such as TCAS IV should be incorporated into a more generic 
system of air-to-air data link for additional applications. As a result of these 
issues, the TCAS IV concept was abandoned as <A title="Automatic dependent surveillance-broadcast" 
href="http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast">ADS-B</A> 
development started.<SUP id="cite_ref-sci_aeronautics_19-1" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-sci_aeronautics-19"><SPAN>[</SPAN>20<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-FAA_TCAS_20-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-FAA_TCAS-20"><SPAN>[</SPAN>21<SPAN>]</SPAN></A></SUP></P>
<H2><SPAN class="editsection">[<A title="Edit section: Current implementation" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=19">edit</A>]</SPAN> 
<SPAN id="Current_implementation" class="mw-headline">Current 
implementation</SPAN></H2>
<P>Although the system occasionally suffers from false alarms, pilots are now 
under strict instructions to regard all TCAS messages as genuine alerts 
demanding an immediate, high-priority response. Windshear Detection and <A 
class="mw-redirect" title="Ground Proximity Warning System" href="http://en.wikipedia.org/wiki/Ground_Proximity_Warning_System">GPWS</A> 
alerts and warnings have higher priority than the TCAS. The <A title="Federal Aviation Administration" 
href="http://en.wikipedia.org/wiki/Federal_Aviation_Administration">FAA</A> and 
most other countries' authorities' rules state that in the case of a conflict 
between TCAS RA and <A title="Air traffic control" href="http://en.wikipedia.org/wiki/Air_traffic_control">air 
traffic control</A> (ATC) instructions, the TCAS RA always takes precedence 
(this is mainly because of the TCAS-RA inherently possessing a more current and 
comprehensive picture of the situation than air traffic controllers, whose <A 
title="Radar" href="http://en.wikipedia.org/wiki/Radar">radar</A>/<A title="Transponder (aviation)" 
href="http://en.wikipedia.org/wiki/Transponder_(aviation)">transponder</A> 
updates usually happen at a much slower rate than the TCAS interrogations).<SUP 
id="cite_ref-TCAS70_0-10" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS70-0"><SPAN>[</SPAN>1<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-TCAS71_1-10" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TCAS71-1"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP> 
If one aircraft follows a TCAS RA and the other follows conflicting ATC 
instructions, a collision can occur, such as the July 1, 2002 <A class="mw-redirect" 
title="Bashkirian Airlines Flight 2937" href="http://en.wikipedia.org/wiki/Bashkirian_Airlines_Flight_2937">Überlingen 
disaster</A>. In this mid-air collision, both airplanes were fitted with TCAS II 
Version 7.0 systems which functioned properly, but one obeyed the TCAS advisory 
while the other ignored the TCAS and obeyed the controller; both aircraft 
descended into a fatal collision.<SUP id="cite_ref-BFUAX001_21-0" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-BFUAX001-21"><SPAN>[</SPAN>22<SPAN>]</SPAN></A></SUP></P>
<P>This accident could have been prevented if TCAS was able to reverse the 
original RA for one of the aircraft when it detects that the crew of the other 
one is not following their original TCAS RA, but conflicting ATC instructions 
instead. This is one of the features that will be implemented within Version 7.1 
of TCAS II.<SUP id="cite_ref-SIRE_13-1" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-SIRE-13"><SPAN>[</SPAN>14<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-22" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-22"><SPAN>[</SPAN>23<SPAN>]</SPAN></A></SUP><SUP 
id="cite_ref-23" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-23"><SPAN>[</SPAN>24<SPAN>]</SPAN></A></SUP></P>
<P>Implementation of TCAS II Version 7.1 has been originally planned to start 
between 2009 and 2011 by retrofitting and forward fitting all the TCAS II 
equipped aircraft, with the goal that by 2014 the version 7.0 will be completely 
phased out and replaced by version 7.1. The <A title="Federal Aviation Administration" 
href="http://en.wikipedia.org/wiki/Federal_Aviation_Administration">FAA</A> and 
<A title="European Aviation Safety Agency" href="http://en.wikipedia.org/wiki/European_Aviation_Safety_Agency">EASA</A> 
have already published the TCAS II Version 7.1 Technical Standard Order 
(TSO-C119c<SUP id="cite_ref-TSO-C119c_24-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-TSO-C119c-24"><SPAN>[</SPAN>25<SPAN>]</SPAN></A></SUP> 
and ETSO-C119c,<SUP id="cite_ref-ETSO-C119c_25-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-ETSO-C119c-25"><SPAN>[</SPAN>26<SPAN>]</SPAN></A></SUP> 
respectively) effective since 2009, based on the RTCA DO-185B<SUP id="cite_ref-DO-185_2-2" 
class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-DO-185-2"><SPAN>[</SPAN>3<SPAN>]</SPAN></A></SUP> 
and EUROCAE ED-143 standards. On 25 September 2009 <A title="Federal Aviation Administration" 
href="http://en.wikipedia.org/wiki/Federal_Aviation_Administration">FAA</A> 
issued Advisory Circular AC 20-151A<SUP id="cite_ref-AC-20-151A_26-0" class="reference"><A 
href="http://en.wikipedia.org/wiki/TCAS#cite_note-AC-20-151A-26"><SPAN>[</SPAN>27<SPAN>]</SPAN></A></SUP> 
providing guidance for obtaining airworthiness approval for TCAS II systems, 
including the new version 7.1. On 5 October 2009 the <A title="Association of European Airlines" 
href="http://en.wikipedia.org/wiki/Association_of_European_Airlines">Association 
of European Airlines (AEA)</A> published a Position Paper<SUP id="cite_ref-AEA-PP_27-0" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-AEA-PP-27"><SPAN>[</SPAN>28<SPAN>]</SPAN></A></SUP> 
showing the need to mandate TCAS II Version 7.1 on all aircraft as a matter of 
priority. On 25 March 2010 the <A title="European Aviation Safety Agency" href="http://en.wikipedia.org/wiki/European_Aviation_Safety_Agency">European 
Aviation Safety Agency (EASA)</A> published Notice of Proposed Amendment (NPA) 
No. 2010-03 pertaining to the introduction of ACAS II software version 7.1.<SUP 
id="cite_ref-ETSO_Dev56_28-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-ETSO_Dev56-28"><SPAN>[</SPAN>29<SPAN>]</SPAN></A></SUP> 
On 14 September 2010 <A title="European Aviation Safety Agency" href="http://en.wikipedia.org/wiki/European_Aviation_Safety_Agency">EASA</A> 
published the Comment Response Document (CRD) to the above mentioned NPA.<SUP 
id="cite_ref-CRD201003_29-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-CRD201003-29"><SPAN>[</SPAN>30<SPAN>]</SPAN></A></SUP> 
Separately, a proposal has been made to amend the <A class="mw-redirect" title="ICAO" 
href="http://en.wikipedia.org/wiki/ICAO">ICAO</A> standard to require TCAS II 
Version 7.1 for compliance with ACAS II SARPs.</P>
<P><A class="mw-redirect" title="ICAO" 
href="http://en.wikipedia.org/wiki/ICAO">ICAO</A> has circulated an amendment 
for formal member state agreement which recommends TCAS II Change 7.1 adoption 
by 1 January 2014 for forward fit and 1 January 2017 for retrofit. Following the 
feedback and comments from airline operators, <A title="European Aviation Safety Agency" 
href="http://en.wikipedia.org/wiki/European_Aviation_Safety_Agency">EASA</A> has 
proposed the following dates for the TCAS II Version 7.1 mandate in European 
airspace: forward fit (for new aircraft) 1 March 2012, retrofit (for existing 
aircraft) 1 December 2015. These dates are proposed dates, subject to further 
regulatory processes, and are not final until the Implementing Rule has been 
published.<SUP id="cite_ref-EUROTCAS71_16-2" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-EUROTCAS71-16"><SPAN>[</SPAN>17<SPAN>]</SPAN></A></SUP></P>
<P>Among the system manufacturers, by February 2010 ACSS<SUP id="cite_ref-ACSS71_30-0" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-ACSS71-30"><SPAN>[</SPAN>31<SPAN>]</SPAN></A></SUP> 
certified Change 7.1 for their TCAS 2000 and Legacy TCAS II systems,<SUP id="cite_ref-ACSSTCAS_31-0" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-ACSSTCAS-31"><SPAN>[</SPAN>32<SPAN>]</SPAN></A></SUP> 
and is currently offering Change 7.1 upgrade for their customers.<SUP id="cite_ref-ACSSUP71_32-0" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-ACSSUP71-32"><SPAN>[</SPAN>33<SPAN>]</SPAN></A></SUP> 
By June 2010 <A title="Honeywell" 
href="http://en.wikipedia.org/wiki/Honeywell">Honeywell</A> published a white 
paper with their proposed solutions for TCAS II Version 7.1.<SUP id="cite_ref-HWTCAS_33-0" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-HWTCAS-33"><SPAN>[</SPAN>34<SPAN>]</SPAN></A></SUP> 
<A title="Rockwell Collins" 
href="http://en.wikipedia.org/wiki/Rockwell_Collins">Rockwell Collins</A> 
currently announces that their TCAS-94, TCAS-4000 and TSS-4100 TCAS II compliant 
systems are software upgradeable to Change 7.1 when available.<SUP id="cite_ref-RCTCAS_34-0" 
class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-RCTCAS-34"><SPAN>[</SPAN>35<SPAN>]</SPAN></A></SUP></P>
<H3><SPAN class="editsection">[<A title="Edit section: Current TCAS Limitations" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=20">edit</A>]</SPAN> 
<SPAN id="Current_TCAS_Limitations" class="mw-headline">Current TCAS 
Limitations</SPAN></H3>
<TABLE class="metadata plainlinks ambox ambox-content ambox-Unreferenced">
  <TBODY>
  <TR>
    <TD class="mbox-image">
      <DIV style="width: 52px;"><A class="image" href="http://en.wikipedia.org/wiki/File:Question_book-new.svg"><IMG 
      alt="Question book-new.svg" src="Traffic%20collision%20avoidance%20system%20-%20Wikipedia,%20the%20free%20encyclopedia_files/50px-Question_book-new.svg.png" 
      width="50" height="39"></A></DIV></TD>
    <TD class="mbox-text">This section <B>does not <A title="Wikipedia:Citing sources" 
      href="http://en.wikipedia.org/wiki/Wikipedia:Citing_sources">cite</A> any 
      <A title="Wikipedia:Verifiability" href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability">references 
      or sources</A></B>. Please help improve this section by adding citations 
      to <A title="Wikipedia:Identifying reliable sources" href="http://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sources">reliable 
      sources</A>. Unsourced material may be <A title="Template:Citation needed" 
      href="http://en.wikipedia.org/wiki/Template:Citation_needed">challenged</A> 
      and <A title="Wikipedia:Verifiability" href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidence">removed</A>. 
      <SMALL><I>(January 2011)</I></SMALL></TD></TR></TBODY></TABLE>
<P>While the safety benefits of current TCAS implementations are self-evident, 
the full technical and operational potential of TCAS is not fully exploited due 
to limitations in current implementations (most of which will need to be 
addressed in order to further facilitate the design and implementation of <A 
title="Free flight (air traffic control)" href="http://en.wikipedia.org/wiki/Free_flight_(air_traffic_control)">Free 
flight</A>):</P>
<UL>
  <LI>TCAS is limited to supporting only vertical separation advisories, more 
  complex traffic conflict scenarios may however be more easily and efficiently 
  remedied by also making use of lateral resolution maneuvers; this applies in 
  particular to traffic conflicts with marginal terrain clearance, or conflict 
  scenarios that are similarly restricted by vertical constraints (e.g. in busy 
  <A class="mw-redirect" title="RVSM" 
  href="http://en.wikipedia.org/wiki/RVSM">RVSM</A> airspace)</LI>
  <LI>ATC can be automatically informed about resolution advisories issued by 
  TCAS only when the aircraft is within an area covered by a Mode S, or an <A 
  title="Automatic dependent surveillance-broadcast" href="http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast">ADS-B</A> 
  monitoring network. In other cases controllers may be unaware of TCAS-based 
  resolution advisories or even issue conflicting instructions (unless ATC is 
  explicitly informed by cockpit crew members about an issued RA during a 
  high-workload situation), which may be a source of confusion for the affected 
  crews while additionally also increasing pilot work load. In May 2009, 
  Luxembourg, Hungary and the Czech Republic show downlinked RAs to 
  controllers.</LI>
  <LI>In the above context, TCAS lacks automated facilities to enable pilots to 
  easily report and acknowledge reception of a (mandatory) RA to ATC (and 
  intention to comply with it), so that voice radio is currently the only option 
  to do so, which however additionally increases pilot and ATC workload, as well 
  as frequency congestion during critical situations.</LI>
  <LI>In the same context, situational awareness of ATC depends on exact 
  information about aircraft maneuvering, especially during conflict scenarios 
  that may possibly cause or contribute to new conflicts by deviating from 
  planned routing, so automatically visualizing issued resolution advisories and 
  recalculating the traffic situation within the affected sector would obviously 
  help ATC in updating and maintaining situational awareness even during 
  unplanned, ad hoc routing changes induced by separation conflicts.</LI>
  <LI>Today's TCAS displays do not provide information about resolution 
  advisories issued to other (conflicting) aircraft, while resolution advisories 
  issued to other aircraft may seem irrelevant to another aircraft, this 
  information would enable and help crews to assess whether other aircraft 
  (conflicting traffic) actually comply with RAs by comparing the actual rate of 
  (altitude) change with the requested rate of change (which could be done 
  automatically and visualized accordingly by modern avionics), thereby 
  providing crucial realtime information for situational awareness during highly 
  critical situations.</LI>
  <LI>TCAS displays today are often primarily range-based, as such they only 
  show the traffic situation within a configurable range of miles/feet, however 
  under certain circumstances a "time-based" representation (i.e. within the 
  next xx minutes) might be more intuitive.</LI>
  <LI>Lack of terrain/ground and obstacle awareness (e.g. connection to <A 
  title="Terrain awareness and warning system" href="http://en.wikipedia.org/wiki/Terrain_awareness_and_warning_system">TAWS</A>, 
  including <A class="mw-redirect" title="Minimum Safety Altitude" href="http://en.wikipedia.org/wiki/Minimum_Safety_Altitude">MSA</A> 
  sector awareness), which might be critical for creating feasible 
  (non-dangerous, in the context of terrain clearance) and useful resolution 
  advisories (i.e. prevent extreme descent instructions if close to terrain), to 
  ensure that TCAS RAs never facilitate <A title="Controlled flight into terrain" 
  href="http://en.wikipedia.org/wiki/Controlled_flight_into_terrain">CFIT</A> 
  (Controlled Flight into Terrain) scenarios.</LI>
  <LI>Aircraft performance in general and current performance capabilities in 
  particular (due to active aircraft configuration) are not taken into account 
  during the negotiation and creation of resolution advisories (as it is the 
  case for differences between different types of aircraft, e.g. turboprop/jet 
  vs. helicopters), so that it is theoretically possible that resolution 
  advisories are issued that demand climb or sink rates outside the normal/safe 
  flight envelope of an aircraft during a certain phase of flight (i.e. due to 
  the aircraft's current configuration). Furthermore, as all traffic is being 
  dealt with equally, there's no distinction taking place between different 
  types of aircraft, neglecting the option of exploiting aircraft-specific 
  (performance) information to issue customized and optimized instructions for 
  any given traffic conflict (i.e. by issuing climb instructions to those 
  aircraft that can provide the best climb rates, while issuing descend 
  instructions to aircraft providing comparatively better sink rates, thereby 
  hopefully maximizing altitude change per time unit, that is separation). As an 
  example, TCAS can order an aircraft to climb when it is already at its service 
  ceiling for its current configuration.<SUP id="cite_ref-35" 
  class="reference"><A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_note-35"><SPAN>[</SPAN>36<SPAN>]</SPAN></A></SUP></LI>
  <LI>TCAS is primarily extrapolation-oriented, as such it is using algorithms 
  trying to approximate 4D trajectory prediction using the "flight path 
  history", in order to assess and evaluate the current traffic situation within 
  an aircraft's proximity, however the degree of data- reliability and 
  usefulness could be significantly improved by enhancing said information with 
  limited access to relevant flight plan information, as well as to relevant ATC 
  instructions to get a more comprehensive picture of other traffic's (route) 
  plans and intentions, so that flight path predictions would no longer be 
  merely based on estimations but rather <I>actual</I> aircraft routing (<A 
  title="FMS" href="http://en.wikipedia.org/wiki/FMS">FMS</A> <A title="Flight plan" 
  href="http://en.wikipedia.org/wiki/Flight_plan">flight plan</A>) and ATC 
  instructions. If TCAS is modified to use data that is used by other systems, 
  care will be required to ensure that the risks of common failure modes are 
  sufficiently small.</LI>
  <LI>TCAS is not fitted to many smaller aircraft mainly due to the high costs 
  involved (between $25,000 and $150,000). Many smaller personal business jets 
  for example, are currently not legally required to have TCAS installed, even 
  though they fly in the same airspace as larger aircraft that are required to 
  have proper TCAS equipment on board. The TCAS system can only perform at its 
  true operational potential once all aircraft in any given airspace have a 
  properly working TCAS unit on board.</LI></UL>
<H3><SPAN class="editsection">[<A title="Edit section: Regulatory situation around the world" 
href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=21">edit</A>]</SPAN> 
<SPAN id="Regulatory_situation_around_the_world" class="mw-headline">Regulatory 
situation around the world</SPAN></H3>
<TABLE class="wikitable">
  <TBODY>
  <TR>
    <TH>Jurisdiction (Agency)</TH>
    <TH>Classification of aircraft</TH>
    <TH>TCAS mode</TH>
    <TH>Date of mandate</TH></TR>
  <TR>
    <TD>USA (<A class="mw-redirect" title="FAA" href="http://en.wikipedia.org/wiki/FAA">FAA</A>)</TD>
    <TD>All commercial turbine-powered transport aircraft with more than 30 
      passenger seats (or MTOW above 33,000&nbsp;lb/15,000&nbsp;kg)</TD>
    <TD>TCAS II</TD>
    <TD>1 January 1993</TD></TR>
  <TR>
    <TD>Europe (<A title="EASA" 
      href="http://en.wikipedia.org/wiki/EASA">EASA</A>)</TD>
    <TD>All civil turbine-powered transport aircraft with more than 30 
      passenger seats (or MTOW above 15,000&nbsp;kg)<SUP id="cite_ref-eurocontrol_36-0" 
      class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-eurocontrol-36"><SPAN>[</SPAN>37<SPAN>]</SPAN></A></SUP></TD>
    <TD>TCAS II</TD>
    <TD>1 January 2000</TD></TR>
  <TR>
    <TD>Europe (<A title="EASA" 
      href="http://en.wikipedia.org/wiki/EASA">EASA</A>)</TD>
    <TD>All civil turbine powered transport aircraft with more than 19 
      passenger seats (or MTOW above 5,700&nbsp;kg)<SUP id="cite_ref-eurocontrol_36-1" 
      class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-eurocontrol-36"><SPAN>[</SPAN>37<SPAN>]</SPAN></A></SUP></TD>
    <TD>ACAS II (Effectively TCAS II Version 7.0)</TD>
    <TD>1 January 2005</TD></TR>
  <TR>
    <TD>Australia (<A title="Civil Aviation Safety Authority" href="http://en.wikipedia.org/wiki/Civil_Aviation_Safety_Authority">CASA</A>)</TD>
    <TD>All commercial turbine powered transport aircraft with more than 30 
      passenger seats (or MTOW above 15,000&nbsp;kg)<SUP id="cite_ref-casa_37-0" 
      class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-casa-37"><SPAN>[</SPAN>38<SPAN>]</SPAN></A></SUP></TD>
    <TD>TCAS II</TD>
    <TD>1 January 2000</TD></TR>
  <TR>
    <TD>Hong Kong, China (<A title="Civil Aviation Department (Hong Kong)" 
      href="http://en.wikipedia.org/wiki/Civil_Aviation_Department_(Hong_Kong)">Civil 
      Aviation Department</A>)</TD>
    <TD>All aircraft in Hong Kong with more than 9 passenger seats (or MTOW 
      greater than 5,700&nbsp;kg)<SUP id="cite_ref-cad_38-0" 
      class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-cad-38"><SPAN>[</SPAN>39<SPAN>]</SPAN></A></SUP></TD>
    <TD>TCAS II Version 7.0</TD>
    <TD>1 January 2000</TD></TR>
  <TR>
    <TD>Brazil (<A title="National Civil Aviation Agency of Brazil" href="http://en.wikipedia.org/wiki/National_Civil_Aviation_Agency_of_Brazil">National 
      Civil Aviation Agency</A>)</TD>
    <TD>All transport category aircraft with more than 30 passenger seats</TD>
    <TD>TCAS II Version 7.0</TD>
    <TD>1 January 2008</TD></TR>
  <TR>
    <TD>Brazil (<A title="National Civil Aviation Agency of Brazil" href="http://en.wikipedia.org/wiki/National_Civil_Aviation_Agency_of_Brazil">National 
      Civil Aviation Agency</A>)</TD>
    <TD>All transport category aircraft with more than 19 passenger seats</TD>
    <TD>TCAS II Version 7.0</TD>
    <TD>1 January 2010</TD></TR>
  <TR>
    <TD>Peru (<A class="new" title="Directorate General of Civil Aviation of Peru (page does not exist)" 
      href="http://en.wikipedia.org/w/index.php?title=Directorate_General_of_Civil_Aviation_of_Peru&amp;action=edit&amp;redlink=1">Dirección 
      General de Aeronáutica Civil</A>)</TD>
    <TD>All civil turbine powered transport aircraft with more than 19 
      passenger seats (or MTOW above 5,700&nbsp;kg))<SUP id="cite_ref-RAP121K_39-0" 
      class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-RAP121K-39"><SPAN>[</SPAN>40<SPAN>]</SPAN></A></SUP><SUP 
      id="cite_ref-RAP135C_40-0" class="reference"><A href="http://en.wikipedia.org/wiki/TCAS#cite_note-RAP135C-40"><SPAN>[</SPAN>41<SPAN>]</SPAN></A></SUP></TD>
    <TD>ACAS II (Effectively TCAS II Version 7.0)</TD>
    <TD>1 January 2005</TD></TR></TBODY></TABLE>
<H2><SPAN class="editsection">[<A title="Edit section: See also" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=22">edit</A>]</SPAN> 
<SPAN id="See_also" class="mw-headline">See also</SPAN></H2>
<UL>
  <LI><A title="Mid-air collision" href="http://en.wikipedia.org/wiki/Mid-air_collision">Mid-air 
  collision</A> (MAC)</LI>
  <LI><A title="Gol Transportes Aéreos Flight 1907" href="http://en.wikipedia.org/wiki/Gol_Transportes_A%C3%A9reos_Flight_1907">Gol 
  Transportes Aéreos Flight 1907</A></LI>
  <LI><A title="1996 Charkhi Dadri mid-air collision" href="http://en.wikipedia.org/wiki/1996_Charkhi_Dadri_mid-air_collision">1996 
  Charkhi Dadri mid-air collision</A>—November 12, 1996</LI>
  <LI><A class="mw-redirect" title="Bashkirian Airlines Flight 2937" href="http://en.wikipedia.org/wiki/Bashkirian_Airlines_Flight_2937">Bashkirian 
  Airlines Flight 2937</A>—July 1, 2002</LI>
  <LI><A title="Bitching Betty" href="http://en.wikipedia.org/wiki/Bitching_Betty">Bitching 
  Betty</A></LI>
  <LI><A title="Ground proximity warning system" href="http://en.wikipedia.org/wiki/Ground_proximity_warning_system">Ground 
  Proximity Warning System</A></LI>
  <LI><A title="Portable Collision Avoidance System" href="http://en.wikipedia.org/wiki/Portable_Collision_Avoidance_System">Portable 
  Collision Avoidance System</A></LI></UL>
<H2><SPAN class="editsection">[<A title="Edit section: References" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=23">edit</A>]</SPAN> 
<SPAN id="References" class="mw-headline">References</SPAN></H2>
<DIV style="list-style-type: decimal; -moz-column-width: 30em; -webkit-column-width: 30em; column-width: 30em;" 
class="reflist references-column-width">
<OL class="references">
  <LI id="cite_note-TCAS70-0">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-1"><SUP><I><B>b</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-2"><SUP><I><B>c</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-3"><SUP><I><B>d</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-4"><SUP><I><B>e</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-5"><SUP><I><B>f</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-6"><SUP><I><B>g</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-7"><SUP><I><B>h</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-8"><SUP><I><B>i</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-9"><SUP><I><B>j</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS70_0-10"><SUP><I><B>k</B></I></SUP></A> 
  <A class="external text" href="http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/nextgen/research_tech_dev/eng_dev_serv/tcas/media/pdf/tcas.pdf" 
  rel="nofollow">Introduction to TCAS II Version 7</A></LI>
  <LI id="cite_note-TCAS71-1">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-1"><SUP><I><B>b</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-2"><SUP><I><B>c</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-3"><SUP><I><B>d</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-4"><SUP><I><B>e</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-5"><SUP><I><B>f</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-6"><SUP><I><B>g</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-7"><SUP><I><B>h</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-8"><SUP><I><B>i</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-9"><SUP><I><B>j</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCAS71_1-10"><SUP><I><B>k</B></I></SUP></A> 
  <A class="external text" href="http://www.faa.gov/documentLibrary/media/Advisory_Circular/TCAS%20II%20V7.1%20Intro%20booklet.pdf" 
  rel="nofollow">Introduction to TCAS II Version 7.1</A></LI>
  <LI id="cite_note-DO-185-2">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-DO-185_2-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-DO-185_2-1"><SUP><I><B>b</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-DO-185_2-2"><SUP><I><B>c</B></I></SUP></A> 
  <A class="external text" href="http://adsb.tc.faa.gov/SC-147.htm" rel="nofollow">FAA 
  DO-185 Materials and RTCA SC-147 Activities</A></LI>
  <LI id="cite_note-DOC9863-6-3">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-DOC9863-6_3-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-DOC9863-6_3-1"><SUP><I><B>b</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-DOC9863-6_3-2"><SUP><I><B>c</B></I></SUP></A> 
  <A class="external text" href="http://www.eurocontrol.int/msa/gallery/content/public/documents/Doc9863_ACAS_Controller_Training_chp6_1.pdf" 
  rel="nofollow">ICAO Document 9863 - Chapter 6</A></LI>
  <LI id="cite_note-4"><B><A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-4">^</A></B> <A class="external text" 
  href="http://www.sisadminov.net/tcas/docs/cas81_pilotguide.pdf" 
  rel="nofollow">Honeywell TCAS System User Manual</A></LI>
  <LI id="cite_note-ACASA-5"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-ACASA_5-0">^</A></B> 
  <A class="external text" href="http://www.eurocontrol.int/msa/gallery/content/public/documents/Safety/WP1.pdf" 
  rel="nofollow">ACAS Programme Work Package 1</A></LI>
  <LI id="cite_note-CP116-6">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-CP116_6-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-CP116_6-1"><SUP><I><B>b</B></I></SUP></A> 
  <A class="external text" href="http://adsb.tc.faa.gov/TCAS/CPs/CP116.pdf" rel="nofollow">Change 
  proposal CP116</A></LI>
  <LI id="cite_note-ADS-B_UAT-7">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-ADS-B_UAT_7-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-ADS-B_UAT_7-1"><SUP><I><B>b</B></I></SUP></A> 
  <A class="external text" href="http://adsb.tc.faa.gov/WG5_Meetings/Meeting1/UAT-WP-1-09.pdf" 
  rel="nofollow">ADS-B System Description for the UAT</A></LI>
  <LI id="cite_note-8"><B><A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-8">^</A></B> <A class="external text" 
  href="http://www.narcap.org/articles/hci_aero.pdf" rel="nofollow">Potential 
  cooperation between TCAS and ASAS</A></LI>
  <LI id="cite_note-TOR_ADS-B-9"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TOR_ADS-B_9-0">^</A></B> 
  <A class="external text" href="http://www.rtca.org/CMS_DOC/TOR%20-%20Initial%20-%20ADS-B%20-%20TCAS%20Relationship.pdf" 
  rel="nofollow">Terms of Reference - Future ADS-B / TCAS Relationships</A></LI>
  <LI id="cite_note-FAA-TCAS-10"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-FAA-TCAS_10-0">^</A></B> 
  <A class="external text" href="http://adsb.tc.faa.gov/TCAS.htm" 
  rel="nofollow">FAA TCAS Home Page</A></LI>
  <LI id="cite_note-11"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-11">^</A></B> 
  <A class="external text" href="http://www.eurocontrol.int/msa/public/standard_page/ACAS_ICAO_Provisions.html" 
  rel="nofollow">ACAS II ICAO Provisions</A></LI>
  <LI id="cite_note-SC-147-12"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-SC-147_12-0">^</A></B> 
  <A class="external text" href="http://www.rtca.org/CMS_DOC/SC-147%20TOR%20Rev9%20-%20PMC%20Approved%20-%2006-10-2010.pdf" 
  rel="nofollow">SC-147 Terms of Reference - Revision 9</A></LI>
  <LI id="cite_note-SIRE-13">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-SIRE_13-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-SIRE_13-1"><SUP><I><B>b</B></I></SUP></A> 
  <A class="external text" href="http://www.eurocontrol.int/msa/gallery/content/public/documents/SIRE+_WP7_69D_v1.2.pdf" 
  rel="nofollow">Decision criteria for regulatory measures on TCAS II version 
  7.1</A></LI>
  <LI id="cite_note-CP112E-14"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-CP112E_14-0">^</A></B> 
  <A class="external text" href="http://adsb.tc.faa.gov/TCAS/CPs/CP112E.pdf" 
  rel="nofollow">Change proposal CP112E</A></LI>
  <LI id="cite_note-CP115-15"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-CP115_15-0">^</A></B> 
  <A class="external text" href="http://adsb.tc.faa.gov/TCAS/CPs/CP115.pdf" rel="nofollow">Change 
  proposal CP115</A></LI>
  <LI id="cite_note-EUROTCAS71-16">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-EUROTCAS71_16-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-EUROTCAS71_16-1"><SUP><I><B>b</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-EUROTCAS71_16-2"><SUP><I><B>c</B></I></SUP></A> 
  <A class="external text" href="http://www.eurocontrol.int/msa/public/standard_page/ACAS_Upcoming_Changes.html" 
  rel="nofollow">EUROCONTROL - TCAS II Version 7.1</A></LI>
  <LI id="cite_note-TCASIII-17"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TCASIII_17-0">^</A></B> 
  <A class="external text" href="http://www.ll.mit.edu/mission/aviation/publications/publication-files/atc-reports/Burgess_1995_ATC-231_WW-15318.pdf" 
  rel="nofollow">Project Report ATC-231</A></LI>
  <LI id="cite_note-skybrary-18"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-skybrary_18-0">^</A></B> 
  <A class="external text" href="http://www.skybrary.aero/index.php/ACAS" rel="nofollow">Skybrary 
  ACAS</A></LI>
  <LI id="cite_note-sci_aeronautics-19">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-sci_aeronautics_19-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-sci_aeronautics_19-1"><SUP><I><B>b</B></I></SUP></A> 
  <A class="external text" href="http://yarchive.net/air/airliners/tcas.html" 
  rel="nofollow">TCAS and Transponders</A></LI>
  <LI id="cite_note-FAA_TCAS-20"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-FAA_TCAS_20-0">^</A></B> 
  <A class="external text" href="http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/nextgen/research_tech_dev/eng_dev_serv/tcas/" 
  rel="nofollow">FAA Engineering Development Services Group - TCAS 
  Support</A></LI>
  <LI id="cite_note-BFUAX001-21"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-BFUAX001_21-0">^</A></B> 
  <A class="external text" href="http://www.bfu-web.de/cln_003/nn_53140/EN/Publications/Investigation_20Report/2002/Report__02__AX001-1-2___C3_9Cberlingen__Report,templateId=raw,property=publicationFile.pdf/Report_02_AX001-1-2_%C3%9Cberlingen_Report.pdf" 
  rel="nofollow">BFU Investigation Report AX001-1-2/02</A></LI>
  <LI id="cite_note-22"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-22">^</A></B> 
  <A class="external text" href="http://www.eurocontrol.int/msa/gallery/content/public/documents/acas/TCAS-SAF-T2-D07_v1.2.pdf" 
  rel="nofollow">TCAS Safety Study - Collision risk due to TCAS safety 
  issues</A></LI>
  <LI id="cite_note-23"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-23">^</A></B> 
  <A class="external text" href="http://www.eurocontrol.int/msa/gallery/content/public/documents/acas/TCAS-SAF-T2-D08_v2.0.pdf" 
  rel="nofollow">TCAS Safety Study - Collision risk due to TCAS safety issues 
  (Presentation)</A></LI>
  <LI id="cite_note-TSO-C119c-24"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-TSO-C119c_24-0">^</A></B> 
  <A class="external text" href="http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgtso.nsf/0/95b393711426c9c78625759b006481ea/$FILE/TSO-C119c.pdf" 
  rel="nofollow">FAA Technical Standard Order TSO-C119c</A></LI>
  <LI id="cite_note-ETSO-C119c-25"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-ETSO-C119c_25-0">^</A></B> 
  <A class="external text" href="http://easa.europa.eu/ws_prod/g/doc/Agency_Mesures/Agency_Decisions/2009/cs_etso_5/Annex%20II%20-%20ETSO.pdf" 
  rel="nofollow">European Technical Standard Order ETSO-C119c</A></LI>
  <LI id="cite_note-AC-20-151A-26"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-AC-20-151A_26-0">^</A></B> 
  <A class="external text" href="http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2020-151A.pdf" 
  rel="nofollow">FAA Advisory Circular AC 20-151A - Airworthiness Approval of 
  Traffic Alert and Collision Avoidance Systems (TCAS II), Versions 7.0 &amp; 
  7.1 and Associated Mode S Transponders</A></LI>
  <LI id="cite_note-AEA-PP-27"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-AEA-PP_27-0">^</A></B> 
  <A class="external text" href="http://hub.easa.europa.eu/crt/docs/viewcrdattachment/cid_41072/aid_460/fmd_3f25c67f0cd4b56f59cb31e18ad71a35" 
  rel="nofollow">AEA Position Paper on TCAS Version 7.1 implementation</A></LI>
  <LI id="cite_note-ETSO_Dev56-28"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-ETSO_Dev56_28-0">^</A></B> 
  <A class="external text" href="http://easa.europa.eu/certification/docs/deviation/ETSO%20DevP%2057.pdf" 
  rel="nofollow">EASA Deviation Request #56</A></LI>
  <LI id="cite_note-CRD201003-29"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-CRD201003_29-0">^</A></B> 
  <A class="external text" href="https://easa.europa.eu/rulemaking/docs/crd/CRD%202010-03.pdf" 
  rel="nofollow">Comment Response Document (CRD) to NPA 2010-03</A></LI>
  <LI id="cite_note-ACSS71-30"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-ACSS71_30-0">^</A></B> 
  <A class="external text" href="http://www.acss.com/change71" 
  rel="nofollow">ACSS Change 7.1 for TCAS II</A></LI>
  <LI id="cite_note-ACSSTCAS-31"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-ACSSTCAS_31-0">^</A></B> 
  <A class="external text" href="http://www.acss.com/SiteCollectionDocuments/Press%20Releases/Change%207-1%20TSO.pdf" 
  rel="nofollow">Press Release - ACSS Certifies Change 7.1 for TCAS 2000 and 
  Legacy TCAS II</A></LI>
  <LI id="cite_note-ACSSUP71-32"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-ACSSUP71_32-0">^</A></B> 
  <A class="external text" href="http://www.acss.com/Advertisements/Change%207-1%20Web%20page.pdf" 
  rel="nofollow">ACSS Change 7.1 for TCAS II flyer</A></LI>
  <LI id="cite_note-HWTCAS-33"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-HWTCAS_33-0">^</A></B> 
  <A class="external text" href="http://www.honeywellairlinesolutions.com/downloads/TCAS.pdf" 
  rel="nofollow">Honeywell Solutions for TCAS II Change 7.1</A></LI>
  <LI id="cite_note-RCTCAS-34"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-RCTCAS_34-0">^</A></B> 
  <A class="external text" href="http://www.rockwellcollins.com/Products_and_Systems/Radar_and_Surveillance/Traffic.aspx" 
  rel="nofollow">Rockwell Collins Traffic surveillance products</A></LI>
  <LI id="cite_note-35"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-35">^</A></B> 
  <A class="external free" href="http://www.airliners.net/aviation-forums/general_aviation/read.main/361350" 
  rel="nofollow">http://www.airliners.net/aviation-forums/general_aviation/read.main/361350</A></LI>
  <LI id="cite_note-eurocontrol-36">^ <A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-eurocontrol_36-0"><SUP><I><B>a</B></I></SUP></A> 
  <A 
  href="http://en.wikipedia.org/wiki/TCAS#cite_ref-eurocontrol_36-1"><SUP><I><B>b</B></I></SUP></A> 
  <A class="external text" href="http://www.eurocontrol.int/msa/public/standard_page/ACAS_Equipage_Requirements.html" 
  rel="nofollow">European ACAS II Mandate</A></LI>
  <LI id="cite_note-casa-37"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-casa_37-0">^</A></B> 
  <A class="external text" href="http://casa.gov.au/download/orders/amend/2001stat348expl.pdf" 
  rel="nofollow">Explanatory Statement regarding TCAS for CASA(PDF)</A></LI>
  <LI id="cite_note-cad-38"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-cad_38-0">^</A></B> 
  <A class="external text" href="http://www.cad.gov.hk/reports/HKAN/AN024%20%20Issue04%20I.pdf" 
  rel="nofollow">Airworthiness Notice No. 24 (PDF)</A></LI>
  <LI id="cite_note-RAP121K-39"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-RAP121K_39-0">^</A></B> 
  <A class="external text" href="http://www.mtc.gob.pe/portal/transportes/aereo/regulaciones/docs/rap_rev17/rap121/rap121_subparte_k_rev%2017.pdf" 
  rel="nofollow">DGAC Perú - RAP 121 - Subpart K (PDF)</A></LI>
  <LI id="cite_note-RAP135C-40"><B><A href="http://en.wikipedia.org/wiki/TCAS#cite_ref-RAP135C_40-0">^</A></B> 
  <A class="external text" href="http://www.mtc.gob.pe/portal/transportes/aereo/regulaciones/docs/rap_rev18/rap135/rap_135_subparte_c_rev17.PDF" 
  rel="nofollow">DGAC Perú - RAP 135 - Subpart C (PDF)</A></LI></OL></DIV>
<H2><SPAN class="editsection">[<A title="Edit section: External links" href="http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&amp;action=edit&amp;section=24">edit</A>]</SPAN> 
<SPAN id="External_links" class="mw-headline">External links</SPAN></H2>
<UL>
  <LI><A class="external text" href="http://www.eurocontrol.int/msa/public/standard_page/ACAS_Startpage.html" 
  rel="nofollow">EUROCONTROL ACAS Website</A></LI>
  <LI><A class="external text" href="http://www.eurocontrol.int/msa/public/standard_page/ACAS_Upcoming_Changes.html" 
  rel="nofollow">TCAS II Version 7.1</A></LI>
  <LI><A class="external text" href="http://www.allstar.fiu.edu/aero/TCAS.htm" 
  rel="nofollow">Discussion of TCAS</A></LI>
  <LI><A class="external text" href="http://www.collisionavoidance.org/" rel="nofollow">AIS-P/TailLight 
  alternative to TCAS and ADS-B without the problems of TCAS and ADS-B</A></LI>
  <LI><A class="external text" href="http://www.airsport-corp.com/adsb2.htm" 
  rel="nofollow">Critical discussion of TCAS using hypothetical abuse/exploit 
  scenarios of TCAS usage</A></LI>
  <LI><A class="external text" href="http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/nextgen/research_tech_dev/eng_dev_serv/tcas/media/pdf/tcas.pdf" 
  rel="nofollow">Introduction to TCAS II Version 7</A></LI>
  <LI><A class="external text" href="http://www.faa.gov/documentLibrary/media/Advisory_Circular/TCAS%20II%20V7.1%20Intro%20booklet.pdf" 
  rel="nofollow">Introduction to TCAS II Version 7.1</A></LI>
  <LI><A class="external text" href="http://www.eurocontrol.int/msa/gallery/content/public/documents/SIRE+_WP7_69D_v1.2.pdf" 
  rel="nofollow">Decision criteria for regulatory measures on TCAS II version 
  7.1</A></LI>
  <LI><A class="external text" href="http://www.skybrary.aero/index.php/Solutions:TCAS" 
  rel="nofollow">TCAS User Interface Awareness video toolkit on 
  Skybrary</A></LI>
  <LI><A class="external text" href="http://www.oilandgasuk.co.uk/downloadabledocs/284/c_Mark_%20Prior.pdf" 
  rel="nofollow">Collision avoidance on the UKCS (TCAS II Trial) by Mark Prior 
  (Bristow)</A></LI>
  <LI><A class="external text" href="http://www.privatefly.com/safety-policy.html" 
  rel="nofollow">Private Jet Safety</A></LI></UL>
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            href="http://en.wikipedia.org/wiki/Hardpoint">Hardpoint</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A class="mw-redirect" title="Horizontal stabilizer" 
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            href="http://en.wikipedia.org/wiki/Strut">Strut</A>&nbsp;<SPAN 
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            style="font-weight: bold;">·</SPAN><A class="mw-redirect" title="Aircraft flight control systems" 
            href="http://en.wikipedia.org/wiki/Aircraft_flight_control_systems#Artificial_feel_devices">Artificial 
            feel</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Autopilot" 
            href="http://en.wikipedia.org/wiki/Autopilot">Autopilot</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Canard (aeronautics)" 
            href="http://en.wikipedia.org/wiki/Canard_(aeronautics)">Canard</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Centre stick" href="http://en.wikipedia.org/wiki/Centre_stick">Centre 
            stick</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Deceleron" 
            href="http://en.wikipedia.org/wiki/Deceleron">Deceleron</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Dive brake" href="http://en.wikipedia.org/wiki/Dive_brake">Dive 
            brake</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Elevator (aircraft)" 
            href="http://en.wikipedia.org/wiki/Elevator_(aircraft)">Elevator</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Elevon" href="http://en.wikipedia.org/wiki/Elevon">Elevon</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Electro-hydrostatic actuator" 
            href="http://en.wikipedia.org/wiki/Electro-hydrostatic_actuator">Electro-hydrostatic 
            actuator</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Flaperon" 
            href="http://en.wikipedia.org/wiki/Flaperon">Flaperon</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Flight control modes (electronic)" 
            href="http://en.wikipedia.org/wiki/Flight_control_modes_(electronic)">Flight 
            control modes</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Fly-by-wire" 
            href="http://en.wikipedia.org/wiki/Fly-by-wire">Fly-by-wire</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Gust lock" href="http://en.wikipedia.org/wiki/Gust_lock">Gust 
            lock</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Rudder" 
            href="http://en.wikipedia.org/wiki/Rudder">Rudder</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Servo tab" href="http://en.wikipedia.org/wiki/Servo_tab">Servo 
            tab</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Side-stick" 
            href="http://en.wikipedia.org/wiki/Side-stick">Side-stick</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Spoiler (aeronautics)" 
            href="http://en.wikipedia.org/wiki/Spoiler_(aeronautics)">Spoiler</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Spoileron" href="http://en.wikipedia.org/wiki/Spoileron">Spoileron</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Stabilator" href="http://en.wikipedia.org/wiki/Stabilator">Stabilator</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Stick pusher" href="http://en.wikipedia.org/wiki/Stick_pusher">Stick 
            pusher</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Stick shaker" 
            href="http://en.wikipedia.org/wiki/Stick_shaker">Stick 
            shaker</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Trim tab" 
            href="http://en.wikipedia.org/wiki/Trim_tab">Trim tab</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Yaw damper" href="http://en.wikipedia.org/wiki/Yaw_damper">Yaw 
            damper</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Wing warping" 
            href="http://en.wikipedia.org/wiki/Wing_warping">Wing 
            warping</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Yoke (aircraft)" 
            href="http://en.wikipedia.org/wiki/Yoke_(aircraft)">Yoke</A></P>
            </DIV></DIV></TD></TR>
        <TR style="height: 2px;">
          <TD></TD></TR>
        <TR>
          <TH style="line-height: 110%;" class="navbox-group" scope="row"><A 
            title="Aerodynamics" href="http://en.wikipedia.org/wiki/Aerodynamics">Aerodynamic</A> 
            and <A title="High-lift device" href="http://en.wikipedia.org/wiki/High-lift_device">high-lift</A><BR>
            devices</TH>
          <TD style="padding: 0px; width: 100%; text-align: left; border-left-width: 2px; border-left-style: solid;" 
          class="navbox-list navbox-odd">
            <DIV style="padding: 0em 0.25em;">
            <DIV>
            <P><A title="Boeing X-53 Active Aeroelastic Wing" href="http://en.wikipedia.org/wiki/Boeing_X-53_Active_Aeroelastic_Wing">Active 
            Aeroelastic Wing</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Adaptive Compliant Wing" 
            href="http://en.wikipedia.org/wiki/Adaptive_Compliant_Wing">Adaptive 
            Compliant Wing</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Blown flap" 
            href="http://en.wikipedia.org/wiki/Blown_flap">Blown 
            flap</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Channel wing" 
            href="http://en.wikipedia.org/wiki/Channel_wing">Channel 
            wing</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Dog-tooth" 
            href="http://en.wikipedia.org/wiki/Dog-tooth">Dog-tooth</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Flap (aircraft)" href="http://en.wikipedia.org/wiki/Flap_(aircraft)">Flap</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Gouge flap" href="http://en.wikipedia.org/wiki/Gouge_flap">Gouge 
            flap</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Gurney flap" 
            href="http://en.wikipedia.org/wiki/Gurney_flap">Gurney 
            flap</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Krueger flaps" 
            href="http://en.wikipedia.org/wiki/Krueger_flaps">Krueger 
            flaps</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Leading edge cuff" 
            href="http://en.wikipedia.org/wiki/Leading_edge_cuff">Leading edge 
            cuff</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Leading edge extension" 
            href="http://en.wikipedia.org/wiki/Leading_edge_extension">LEX</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Leading edge slats" 
            href="http://en.wikipedia.org/wiki/Leading_edge_slats">Slats</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Leading edge slot" 
            href="http://en.wikipedia.org/wiki/Leading_edge_slot">Slot</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Stall strips" href="http://en.wikipedia.org/wiki/Stall_strips">Stall 
            strips</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Strake (aviation)" 
            href="http://en.wikipedia.org/wiki/Strake_(aviation)">Strake</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Variable-sweep wing" 
            href="http://en.wikipedia.org/wiki/Variable-sweep_wing">Variable-sweep 
            wing</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Vortex generator" 
            href="http://en.wikipedia.org/wiki/Vortex_generator">Vortex 
            generator</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Vortilon" 
            href="http://en.wikipedia.org/wiki/Vortilon">Vortilon</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Wing fence" href="http://en.wikipedia.org/wiki/Wing_fence">Wing 
            fence</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Wingtip device" 
            href="http://en.wikipedia.org/wiki/Wingtip_device">Winglet</A></P>
            </DIV></DIV></TD></TR>
        <TR style="height: 2px;">
          <TD></TD></TR>
        <TR>
          <TH style="line-height: 110%;" class="navbox-group" scope="row"><A 
            title="Avionics" 
            href="http://en.wikipedia.org/wiki/Avionics">Avionic</A> and <A 
            title="Flight instruments" href="http://en.wikipedia.org/wiki/Flight_instruments">flight<BR>
            instrument</A> systems</TH>
          <TD style="padding: 0px; width: 100%; text-align: left; border-left-width: 2px; border-left-style: solid;" 
          class="navbox-list navbox-even">
            <DIV style="padding: 0em 0.25em;">
            <DIV>
            <P><A title="Airborne collision avoidance system" href="http://en.wikipedia.org/wiki/Airborne_collision_avoidance_system">ACAS</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Air data computer" 
            href="http://en.wikipedia.org/wiki/Air_data_computer">Air data 
            computer</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Airspeed indicator" 
            href="http://en.wikipedia.org/wiki/Airspeed_indicator">Airspeed 
            indicator</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Altimeter" 
            href="http://en.wikipedia.org/wiki/Altimeter">Altimeter</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Annunciator panel" 
            href="http://en.wikipedia.org/wiki/Annunciator_panel">Annunciator 
            panel</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Attitude indicator" 
            href="http://en.wikipedia.org/wiki/Attitude_indicator">Attitude 
            indicator</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Compass" 
            href="http://en.wikipedia.org/wiki/Compass">Compass</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Course Deviation Indicator" 
            href="http://en.wikipedia.org/wiki/Course_Deviation_Indicator">Course 
            Deviation Indicator</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A class="mw-redirect" title="Electronic Flight Instrument System" 
            href="http://en.wikipedia.org/wiki/Electronic_Flight_Instrument_System">EFIS</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A class="mw-redirect" title="Engine Indicating and Crew Alerting System" 
            href="http://en.wikipedia.org/wiki/Engine_Indicating_and_Crew_Alerting_System">EICAS</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Flight data recorder" 
            href="http://en.wikipedia.org/wiki/Flight_data_recorder">Flight data 
            recorder</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Flight management system" 
            href="http://en.wikipedia.org/wiki/Flight_management_system">Flight 
            management system</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Glass cockpit" href="http://en.wikipedia.org/wiki/Glass_cockpit">Glass 
            cockpit</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Global Positioning System" 
            href="http://en.wikipedia.org/wiki/Global_Positioning_System">GPS</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Heading indicator" 
            href="http://en.wikipedia.org/wiki/Heading_indicator">Heading 
            indicator</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Horizontal situation indicator" href="http://en.wikipedia.org/wiki/Horizontal_situation_indicator">Horizontal 
            situation indicator</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Inertial navigation system" 
            href="http://en.wikipedia.org/wiki/Inertial_navigation_system">INAS</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A class="mw-redirect" title="Traffic Collision Avoidance System" 
            href="http://en.wikipedia.org/wiki/Traffic_Collision_Avoidance_System">TCAS</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Transponder (aviation)" 
            href="http://en.wikipedia.org/wiki/Transponder_(aviation)">Transponder</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Turn and bank indicator" 
            href="http://en.wikipedia.org/wiki/Turn_and_bank_indicator">Turn and 
            bank indicator</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Pitot-static system" href="http://en.wikipedia.org/wiki/Pitot-static_system">Pitot-static 
            system</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Radar altimeter" 
            href="http://en.wikipedia.org/wiki/Radar_altimeter">Radar 
            altimeter</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Variometer" 
            href="http://en.wikipedia.org/wiki/Variometer">Vertical Speed 
            Indicator</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Yaw string" 
            href="http://en.wikipedia.org/wiki/Yaw_string">Yaw string</A></P>
            </DIV></DIV></TD></TR>
        <TR style="height: 2px;">
          <TD></TD></TR>
        <TR>
          <TH style="line-height: 110%;" class="navbox-group" scope="row"><A 
            title="Aircraft engine" href="http://en.wikipedia.org/wiki/Aircraft_engine">Propulsion</A> 
            controls,<BR>devices and <A class="mw-redirect" title="Fuel system" 
            href="http://en.wikipedia.org/wiki/Fuel_system">fuel systems</A></TH>
          <TD style="padding: 0px; width: 100%; text-align: left; border-left-width: 2px; border-left-style: solid;" 
          class="navbox-list navbox-odd">
            <DIV style="padding: 0em 0.25em;">
            <DIV>
            <P><A title="Autothrottle" href="http://en.wikipedia.org/wiki/Autothrottle">Autothrottle</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Drop tank" href="http://en.wikipedia.org/wiki/Drop_tank">Drop 
            tank</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="FADEC" 
            href="http://en.wikipedia.org/wiki/FADEC">FADEC</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Fuel tank" href="http://en.wikipedia.org/wiki/Fuel_tank#Aircraft">Fuel 
            tank</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Gascolator" 
            href="http://en.wikipedia.org/wiki/Gascolator">Gascolator</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Inlet cone" href="http://en.wikipedia.org/wiki/Inlet_cone">Inlet 
            cone</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Intake ramp" 
            href="http://en.wikipedia.org/wiki/Intake_ramp">Intake 
            ramp</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="NACA cowling" 
            href="http://en.wikipedia.org/wiki/NACA_cowling">NACA 
            cowling</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Self-sealing fuel tank" 
            href="http://en.wikipedia.org/wiki/Self-sealing_fuel_tank">Self-sealing 
            fuel tank</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Throttle" 
            href="http://en.wikipedia.org/wiki/Throttle">Throttle</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Thrust lever" href="http://en.wikipedia.org/wiki/Thrust_lever">Thrust 
            lever</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Thrust reversal" 
            href="http://en.wikipedia.org/wiki/Thrust_reversal">Thrust 
            reversal</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Townend ring" 
            href="http://en.wikipedia.org/wiki/Townend_ring">Townend 
            ring</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Wet wing" 
            href="http://en.wikipedia.org/wiki/Wet_wing">Wet wing</A></P></DIV>
            </DIV></TD></TR>
        <TR style="height: 2px;">
          <TD></TD></TR>
        <TR>
          <TH style="line-height: 110%;" class="navbox-group" 
            scope="row">Landing and arresting gear</TH>
          <TD style="padding: 0px; width: 100%; text-align: left; border-left-width: 2px; border-left-style: solid;" 
          class="navbox-list navbox-even">
            <DIV style="padding: 0em 0.25em;">
            <DIV>
            <P><A title="Autobrake" href="http://en.wikipedia.org/wiki/Autobrake">Autobrake</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Conventional landing gear" 
            href="http://en.wikipedia.org/wiki/Conventional_landing_gear">Conventional 
            landing gear</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Tailhook" 
            href="http://en.wikipedia.org/wiki/Tailhook">Arrestor 
            hook</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Drogue parachute" 
            href="http://en.wikipedia.org/wiki/Drogue_parachute">Drogue 
            parachute</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Landing gear extender" href="http://en.wikipedia.org/wiki/Landing_gear_extender">Landing 
            gear extender</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Tricycle gear" href="http://en.wikipedia.org/wiki/Tricycle_gear">Tricycle 
            gear</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Tundra tire" 
            href="http://en.wikipedia.org/wiki/Tundra_tire">Tundra 
            tire</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Undercarriage" 
            href="http://en.wikipedia.org/wiki/Undercarriage">Undercarriage</A></P>
            </DIV></DIV></TD></TR>
        <TR style="height: 2px;">
          <TD></TD></TR>
        <TR>
          <TH style="line-height: 110%;" class="navbox-group" 
            scope="row">Escape systems</TH>
          <TD style="padding: 0px; width: 100%; text-align: left; border-left-width: 2px; border-left-style: solid;" 
          class="navbox-list navbox-odd">
            <DIV style="padding: 0em 0.25em;">
            <DIV>
            <P><A title="Ejection seat" href="http://en.wikipedia.org/wiki/Ejection_seat">Ejection 
            seat</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Escape crew capsule" 
            href="http://en.wikipedia.org/wiki/Escape_crew_capsule">Escape crew 
            capsule</A></P></DIV></DIV></TD></TR>
        <TR style="height: 2px;">
          <TD></TD></TR>
        <TR>
          <TH style="line-height: 110%;" class="navbox-group" 
            scope="row">Other systems</TH>
          <TD style="padding: 0px; width: 100%; text-align: left; border-left-width: 2px; border-left-style: solid;" 
          class="navbox-list navbox-even">
            <DIV style="padding: 0em 0.25em;">
            <DIV>
            <P><A title="Aircraft lavatory" href="http://en.wikipedia.org/wiki/Aircraft_lavatory">Aircraft 
            lavatory</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Auxiliary power unit" 
            href="http://en.wikipedia.org/wiki/Auxiliary_power_unit">Auxiliary 
            power unit</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Bleed air" 
            href="http://en.wikipedia.org/wiki/Bleed_air">Bleed air 
            system</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Deicing boot" 
            href="http://en.wikipedia.org/wiki/Deicing_boot">Deicing 
            boot</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Emergency oxygen system" 
            href="http://en.wikipedia.org/wiki/Emergency_oxygen_system">Emergency 
            oxygen system</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            class="mw-redirect" title="Environmental Control System" href="http://en.wikipedia.org/wiki/Environmental_Control_System">Environmental 
            Control System</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Hydraulic fluid" href="http://en.wikipedia.org/wiki/Hydraulic_fluid#Aircraft_hydraulic_systems">Hydraulic 
            system</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Ice protection system" 
            href="http://en.wikipedia.org/wiki/Ice_protection_system">Ice 
            protection system</A>&nbsp;<SPAN 
            style="font-weight: bold;">·</SPAN><A title="Aircraft landing lights" 
            href="http://en.wikipedia.org/wiki/Aircraft_landing_lights">Landing 
            lights</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Navigation light" 
            href="http://en.wikipedia.org/wiki/Navigation_light">Navigation 
            light</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A title="Passenger service unit" 
            href="http://en.wikipedia.org/wiki/Passenger_service_unit">Passenger 
            service unit</A>&nbsp;<SPAN style="font-weight: bold;">·</SPAN><A 
            title="Ram air turbine" href="http://en.wikipedia.org/wiki/Ram_air_turbine">Ram 
            air turbine</A></P></DIV></DIV></TD></TR></TBODY></TABLE></TD></TR>
</TBODY></TABLE>
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    <TD style="padding: 2px;">
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        <TBODY>
        <TR>
          <TH class="navbox-title" colSpan="2" scope="col"><SPAN class="noprint plainlinks navbar"><SPAN 
            style="word-spacing: -0.12em; white-space: nowrap;"><A title="Template:Aviation lists" 
            href="http://en.wikipedia.org/wiki/Template:Aviation_lists"><SPAN 
            style="border: currentColor;" 
            title="View this template">v</SPAN></A> <SPAN style="border: currentColor;"><B>·</B></SPAN> 
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            <DIV style="font-size: 110%;">Lists relating to <A title="Aviation" 
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          <TD></TD></TR>
        <TR>
          <TH class="navbox-group" scope="row">General</TH>
          <TD style="padding: 0px; width: 100%; text-align: left; border-left-width: 2px; border-left-style: solid;" 
          class="navbox-list navbox-odd hlist">
            <DIV style="padding: 0em 0.25em;">
            <UL>
              <LI><A title="List of aircraft" href="http://en.wikipedia.org/wiki/List_of_aircraft">Aircraft</A> 
              (<A title="List of aircraft manufacturers" href="http://en.wikipedia.org/wiki/List_of_aircraft_manufacturers">manufacturers</A>)</LI>
              <LI><A title="List of aircraft engines" href="http://en.wikipedia.org/wiki/List_of_aircraft_engines">Aircraft 
              engines</A> (<A title="List of aircraft engine manufacturers" 
              href="http://en.wikipedia.org/wiki/List_of_aircraft_engine_manufacturers">manufacturers</A>)</LI>
              <LI><A title="List of airlines" href="http://en.wikipedia.org/wiki/List_of_airlines">Airlines</A> 
              (<A title="List of defunct airlines" href="http://en.wikipedia.org/wiki/List_of_defunct_airlines">defunct</A>)</LI>
              <LI><A title="List of airports" href="http://en.wikipedia.org/wiki/List_of_airports">Airports</A></LI>
              <LI><A title="List of civil aviation authorities" href="http://en.wikipedia.org/wiki/List_of_civil_aviation_authorities">Civil 
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